The headaches came first. "Terrible" migraines that would last throughout the day.

Osmond Nicholas, then 26, was working as a police officer in his hometown of Oceanside, California, after earning his Bachelor's degree in criminal justice and his Master's in homeland security at San Diego State University.

While out on the job in May 2017, the former college football player had what he described as "a little blackout" moment while driving his police car. He said he remembers questioning where he was at the moment, and his partner at the time reminded him, "Oh, you're driving right behind me."

The headaches and blackouts persisted. Soon he was sleeping up to 16 hours a day.

In July, after multiple doctors told him it was likely fatigue due to his graveyard shift on the police force, he received a diagnosis that would change the course of his life.

Nicholas was diagnosed with stage 4 glioblastoma multiforme, a rare disease that experts say is among the deadliest type of brain cancers. The aggressive cancer affects an estimated 13,000 in the United States every year and is not curable. Senators John McCain and Ted Kennedy were both diagnosed with and ultimately died from the disease.

Bachelor party plans end up in the emergency room

Before receiving his brain cancer diagnosis, Nicholas said he thought the migraines and chronic fatigue were due to his "work schedule or diet." He changed his diet to see if that would make a difference, but the migraines continued.

"Finally I said, you know what, maybe I am behind in sleep. I went to a doctor, and he kind of gave me the chronic fatigue syndrome diagnosis," he said. But Nicholas didn't understand the diagnosis because he felt like he was getting plenty of sleep.

In June, Nicholas was planning to go to Las Vegas for his bachelor party with some friends. He had proposed to his then-fiancée Trinity Daniel in June 2016, and the two were planning to get married in September 2017. At his parents' home the night before his trip, he experienced an extremely painful headache. "That was the worst headache I ever had, which led to nausea and me waking vomiting," he remembered.

His mother, a nurse practitioner, insisted they go to the hospital immediately.

Within an hour while at the emergency room at Kaiser Permanente Zion Medical Center in San Diego, Nicholas was told that a CT scan showed he had a mass in his brain. "I didn't know what mass was, or I didn't put two and two together -- mass, tumor, cancer," he said.

PHOTO: A scan of Nicholas' brain, taken in June 2017, displayed a tumor that required emergency surgery.
Osmond Nicholas
A scan of Nicholas' brain, taken in June 2017, displayed a tumor that required emergency surgery.

"I was actually excited at this point because for half a year I'd been feeling like I was crazy with these headaches," he continued. "Finally they had found something that I wasn't crazy, and everybody was believing me."

Grasping the reality of his diagnosis

After discovering the mass, Nicholas was told he would have to have emergency surgery that morning. He said the immediacy of the surgery didn't allow him time to digest any of the information.

"At that point, I hadn't even really put cancer in any of this," he said. "I just thought, OK, I got a tumor, or a mass. The worst part at that point was them doing a craniotomy and opening my skull."

After the surgery, he thought he was "over the largest hill." "I was pretty sure that they were going to call me, say no news is good news ... and that did not happen," he shared. He remembered telling his boss that he could come back to work in a few weeks after the staples were removed from his head.

PHOTO: Osmond Nicolas appears in this photo following his emergency brain surgery in June, 2017.
Trinity Daniel
Osmond Nicolas appears in this photo following his emergency brain surgery in June, 2017.

Two weeks post-operation, Nicholas had his first oncology referral appointment in July 2017. There he was told that he had brain cancer, specifically stage 4 glioblastoma, which he described as, "a bunch of words," to him at that point.

"I was probably a little naive, even after having brain surgery, I was of the mindset that people always have benign brain tumors all the time, or benign tumors, I always see it on the news," he said. "That's the extent of it. They take something out of my head, I'll have to deal with the ugly scar, and I'll be back to work."

His mother asked about his prognosis in the appointment after hearing the diagnosis. "That's when the doctor kind of reluctantly, but truthfully, told me the average can be anywhere from 12 to 18 months, but that I was lucky that I got the tumor out," he said.

Although glioblastoma is more common with older adults, the disease affects patients of all ages.

"A lot of research is ongoing trying to understand why these tumors develop and so far, with very rare exception, there does not seem to be any link with environmental exposure, nor with any link for an inherited or genetic predisposition to the development of these tumors," Dr. David Reardon, clinical director, Center for Neuro-Oncology, Medical Oncology, at the Dana-Farber Cancer Institute, told "Good Morning America."

"For the vast majority of patients, this is a type of cancer that develops for reasons we don't understand and is not due to anything they did, or were exposed to or inherited," Reardon, who has no connection to Nicholas' case, said.

With survival rates varying by several prognostic factors, including age, tumor stage and more, the median survival rate is estimated at 15 months for patients with glioblastoma, according to Reardon.

Dr. Michael Vogelbaum, chief of neurosurgery and program leader of the department of neuro-oncology at Moffitt Cancer Center, said for patients who receive "very intensive and highly monitored care" the median survival ranges from around 16 to 20 months. Vogelbaum has no connection to Nicholas' case.

Nicholas said the day he received his diagnosis was "probably one of the hardest days" of his life.

"I literally thought, I'm young, I have cancer -- that means they could probably give me the most chemotherapy and most radiation and I'll be fine," he said. "Then my oncologist later broke it down that this is not that type of cancer; It's a terminal cancer," he remembered. "Sometime sooner or later it will come back."

He remembered crying and not wanting to tell his diagnosis to his fiancée, who had just graduated from law school and was studying for the bar exam. "I just wanted to come back home and report good news ... All I was seeing was that they give you 12 to 15 months ... and they lost their frame of speech ... their sense of way," he said about his research on the disease.

Nicholas called up his close friends to tell them he, "probably wouldn't be here much longer" after hearing the news. "When you're so young, just hearing the word 'terminal means you're gonna die ... I couldn't even mask how that was," he said.

Daniel, Nicholas' then-fiancée, now-wife, said the time was "extremely hard" as a young couple and changed their perspective on life. "We definitely had our sad days where we would just sit around the house and cry, or one thing we used to do together is, which we still do now, we go on really long walks," she said. "We would just kind of talk about how we were feeling. At first, it was hard, but he is a fighter. He is someone who is committed to living."

Moving forward with treatment

Nicholas started his treatment with the standard of care for brain cancer patients. Following surgery, he started Temozolomide, or Temodar, a form of chemotherapy, combined with radiation at UCSD's Moores Cancer Center in August 2017.

But his body did "not respond well" to the chemotherapy. "During radiation, my blood work, which are all my white blood cells, platelets and red blood cells, took a dive, which happens because that's what chemotherapy does," he said.

"Typically they take you off of that for a couple of weeks, it comes back up and then you restart your medication, but mine went so low," he continued. "I remember my platelets were in the single digits, which could cause you to start hemorrhaging and your body basically to die from that."

Nicholas had to discontinue chemotherapy after four weeks because of his body's reaction. He was nearly halfway through his 30 radiation treatments when his doctor informed him that he was "extremely anemic" and he had a very weak immune system.

He remembered getting short of breath from time to time, and his doctor told him, "You have no immune system ... all your neutrophils are at zero, so be careful. Don't go outside.'" The next day, Nicholas got a fever and went straight to the emergency room at Kaiser Permanente Zion Medical Center, where the medical staff placed him in isolation on the oncology unit.

Nicholas was set to get married the next month, on Sept. 9, 2017, and had to stay quarantined on the oncology floor of the hospital for nearly three weeks.

"Up until September, I think third or fourth, they had to wait till my white blood cell neutrophil count got to at least 500 before they could release me out into the public. I remember, at that point, thinking that I was going to cancel my wedding because I was stuck in a hospital," he said. His neutrophil count slowly rose, and he was finally released from the hospital three days before his wedding.

PHOTO: Osmond Nicholas and Trinity Daniel got married on September 9, 2017 in San Diego.
Javier Nicholas
Osmond Nicholas and Trinity Daniel got married on September 9, 2017 in San Diego.

He hasn't done chemotherapy since, though he did finish his radiation treatments. The primary treatment he has relied on since September 2017 is Optune, a cap that he said he wears up to 23 hours a day.

Optune is a device used to treat glioblastoma that, "uses technology called 'tumor treating fields' to deliver electric fields to the brain, which can help stop the proliferation of cancer cells," according to the Mayo Clinic.

Although patients using Optune do not feel any of the electrical impulses from the treatment, Reardon said the treatment takes a "fairly motivated patient" because it should be worn at least 18 hours a day.

"We know from laboratory research that cancer cells, they tend to grow and divide in a very dysregulated and rapid way compared to normal cells in our body," Dr. Reardon explained. "When cancer cells are exposed to these oscillating electrical fields, it makes it very hard for the cells to split in two and divide. Eventually, if they can't do that the cancer cells give up and die."

When Nicholas first learned about the FDA-approved device, he recalled thinking, "If the cap's going to make me live longer, I'll shave my head and we'll do what we have to do."

Along with Optune, Nicholas continues getting platelet transfusions and white blood cell shots to boost his immune system. His blood work is checked every two weeks now and he has scans on his brain every six weeks. "That's really in my life the only time that I really get an active reminder that I have brain cancer," he said on the scans. "Those couple days between getting your MRI ... and your doctor calling you back are probably the more nerve wracking days of your month."

He said he is aware of warnings from doctors about the unpredictability of the tumor. "It could go away ... you don't have anything for 10 years, and then 10 years down the road, something pops up and you have a recurrence of all these cancer cells ... or it could be really quick. But what they do know is that right now ... it will come back."

Reardon said glioblastoma differs from other aggressive cancers because it does not metastasize throughout other body systems. "Although we don't have to worry about the cancer spreading to the lungs, or bones, or lymph nodes, or the liver -- other organs in the body -- it does microscopically spread outwards," he said.

"The main mass that we can see on an MRI scan of the patient when they come in with their deficits or headache procedure, we see a localized mass on the MRI scan, extending outwardly from the mass are microscopic infiltrative cells that are moving outward into the adjacent brain tissues," he continued. "So although it doesn't metastasize and spread out of the brain, it does spread within the brain itself."

Life as a father and husband with brain cancer

Choosing to have a family, Nicholas says, was one of the biggest decisions he made in prioritizing living over his diagnosis. "I didn't really know if I wanted to go through with getting married and put my wife [through becoming] a widow and have a daughter and let her grow up without dad if things went south or how they said it's supposed to go," he said. "It was kind of my first leap of faith that I'm going to live my life and live without boundaries and not let cancer take me a day before."

PHOTO: Osmond Nicholas appears in an undated photo with his daughter Riyah.
Trinity Daniel
Osmond Nicholas appears in an undated photo with his daughter Riyah.

"I believe if I would have said, 'Hey, I don't want to have a baby or anything,' just the stuff that me and my wife kind of planned for -- that we knew we both wanted -- then I'd be letting cancer win that battle of me living my life," he added.

Daniel said she was hesitant to have a child because of her worries about her husband's illness. "I don't want to do this by myself," she remembered thinking. However, she said she and her husband built an even stronger bond early on through their struggles.

"Having such a big test early on in our marriage ... we kind of built the foundation that we're going to stick through this and stick together and whatever comes our way we can figure it out because we've been figuring it out ever since then," she said.

The couple welcomed their daughter Riyah in November 2018, and Daniel said their little girl and her father are inseparable.

PHOTO: Osmond Nicholas appears in this undated photo with his wife Trinity Daniel and their daughter Riyah, who is 18 months old.
Javier Nicholas
Osmond Nicholas appears in this undated photo with his wife Trinity Daniel and their daughter Riyah, who is 18 months old.

"He was more excited, I think, to be a dad, especially when she was born," she said. "I work usually outside of the home, so he's the one that's here with her during the day. He does everything -- meals, diapers. I credit him with her learning how to walk and talk because I wasn't there and she was home with him."

"She's his little roadie, she goes everywhere with him," Daniel added. "They go on hikes, to shopping, to his friends' houses. Anywhere he goes, she goes and he is an amazingly doting father."

After retiring from the police force in October 2019, Nicholas said he has time to devote to his daughter. "I just try to even think of it this way -- even if I do go in five years, six years, which I'm hoping I don't ... there are kids out there and little daughters out there that don't have many days with their father -- and he's alive. So I say, hey, now I can give her all my time."

PHOTO:  In this May 2020, photo, Osmond Nicholas is shown with his 18 month old daughter, Riyah.
Osmond Nicholas
In this May 2020, photo, Osmond Nicholas is shown with his 18 month old daughter, Riyah.

"I'm sure there's going to come a time when she's going to ask about everything, and I think I'm just going to keep it frank and honest because I think that's the best way to go about it," he added.

He said he has trouble putting the joys of fatherhood into words and encourages anyone considering having children to do so, with or without illness. "If you're thinking about it, no matter how bad it is ... it'll be all right," he said. "Whether you're here or not -- just don't let don't let cancer dictate the rest of your life before it has to."

Nicholas is also fortunate to have parents supporting him at all times, he said. "My mom and dad, they've been to every appointment. They also have been rocks in my life as far as just opening my eyes to just surviving really."

His two siblings, Javier Nicholas, 30, and Nadya Hall, 34, have been with him throughout his fight as well.

His older brother Javier Nicholas said he's "extremely proud" of Osmond. "He could have given up and nobody would be able to fault him for that, but he never did," he said. "His life changed forever in one day and he has always handled it like a warrior. He's my hero and an inspiration to those fighting their battle with brain cancer. As his brother, I love him and am truly inspired by his determination and grit."

Along with relying on the support of his family, Osmond Nicholas also uses music as an outlet to cope with his pain. "Once I got out of the hospital and was able to play, it just took me away from the diagnosis for a moment and got me into a different zone of saying just appreciate the music and appreciate that you're here and you can still do the things you love to do," he said.

He said he now shares videos of his guitar playing on Instagram to bring hope to others who might also be fighting glioblastoma.

"I put up more videos not because I think I'm the best guitarist, trust me, I know I'm not, but because I know there's somebody else with glioblastoma, or whatever type of cancer ... that can get encouraged. Because I do think your attitude makes up a lot of how you fare because your mental health needs to be right."

"I don't like to post too many sad things -- not that they don't happen -- but I think it just could be an inspiration that hey, if this guy with a brain tumor is enjoying life, what do we really have to be upset about?"

Raising awareness and living every day to the fullest

The month of May is National Brain Cancer Awareness month, and Nicholas said he believes there is a desperate need for more awareness around brain cancer, specifically glioblastoma.

"I don't think many people think of, know what a glioblastoma is or really know much about brain cancers in general," he said. Nicholas said living with brain cancer gives him the responsibility to share his story and hopes others battling the disease will do the same.

"I'm always going to be an ambassador for it," he said of his illness. "I just think speaking out on it would help out and then being as active as you can, whether it's to your hospitals or down to the senators to get money because funding is where big things actually happen."

Vogelbaum said research for glioblastoma treatment is difficult for several reasons. "There's really no other area of cancer drug development where you don't take samples of treated tissue to understand what the treatment is doing," he said. "It's harder for us to do that in glioblastoma patients, but that is still necessary nonetheless."

He said "direct delivery of therapeutics to the brain" is also necessary. "There needs to be an understanding that there is no way to establish a timeline to success in any field of medicine, particularly in cancer," he explained. Vogelbaum said that in past decades, melanoma was the other untreatable cancer that produced many "terrible and unpredictable outcomes."

"Then along came immunotherapy and targeted therapy, BRAF targeted therapy, and that's completely changed the way that we approach melanoma, to the point where for many patients now it's a very treatable disease," he continued. "That happened in a very short time when there were a lot of other things have been tried and failed. Eventually, the right thing was found. We have to have the same kind of optimistic approach to glioblastoma."

He said researchers must continue to keep trying new approaches to further understand the biology of this cancer.

PHOTO: In this May 2020, photo, Osmond Nicholas and his wife Trinity Daniel, are shown with their 18 month old daughter, Riyah.
Osmond Nicholas
In this May 2020, photo, Osmond Nicholas and his wife Trinity Daniel, are shown with their 18 month old daughter, Riyah.

Nicholas' diagnosis has completely changed his perspective on life. "I've become a little more introspective and just become much more at peace with life in general," he said. "Some people focus on, 'Oh, I just want to live to 100 years' and all that. I feel like being diagnosed with glioblastoma ... I just want to live to have a great day today and live as long as I can. Just to take advantage of that."

His illness has also reinforced his understanding of the fragility of life.

"The only thing I can guarantee is that we're all going to die, so use what you have," he added. "There's a little thing that we used in the brain tumor group, we call like, 'the best group that we never want to ever be a part of,' and I totally wouldn't want to be a part of this group if I could not, but since I am, it has changed my life."

PHOTO: Osmond Nicholas appears in an undated photo with his daughter Riyah.
Trinity Daniel
Osmond Nicholas appears in an undated photo with his daughter Riyah.

"I don't think I see things rosier, but I think I see it more as the perspective of it all comes back to -- you can die any day, so live your life for each day, every day."