The Death Trooper stood in the warm Florida sun, crying behind his mask.

“I’m glad I have a helmet on,” the trooper said, choking on his words.

“This is where my son passed away,” he added, pointing to the looming building behind him. “I haven’t been back here since he passed away. It’s gonna be hard because it’s something I want to face. I need to face it moving on.”

Inside the costume was Andrew McClary, a Florida resident who lost his 19-year-old son, Nicholas, to a rare bone cancer late last year. McClary and his son were both huge "Star Wars" fans and even tried building an R2-D2 robot together until it became too difficult for the increasingly weak Nicholas to help.

Nicholas fought his aggressive bone cancer -- Ewings sarcoma -- for three years, and spent many long days and nights in the Joe DiMaggio Children's Hospital in Hollywood. While there, a group of "Star Wars" cosplayers who visit sick children came to Nicholas’ bedside to entertain him. The group, called the 501st Legion, is made up of fans from around the world who dedicate their spare time to making the world a better place, all while dressing up as evil "Star Wars" characters – in essence, bad guys doing good.

“While the 501st was initially founded to unite costumers with a penchant for 'Star Wars' villainy, one of our real-world missions is to bring good to our communities through volunteer charity work,” said Jason Maston, senior public relations officer of the 501st Legion. “The 501st is always looking for opportunities to brighten the lives of the less fortunate, and to bring awareness to positive causes on both a local and global scale.”

After seeing so many bedridden children brighten at the sight of Darth Vader stalking the halls of a hospital wing, McClary was inspired to join the group himself.

“There’s a real power there,” said McClary. “These are kids that are fighting for their lives and cheering them up and seeing us in costume -- it means a lot. It is important.”

He continued his work with the charity organization after Nicholas’ death and just last week, with members of his own 501st garrison accompanying him in costume, McClary finally returned to the hospital where his son was transferred and later lost his battle with cancer -- the Holtz Children’s Hospital in Miami.

“Come on guys,” said McClary, beckoning for his friends, Kylo Ren, R2D2 and Darth Vader, to follow him through the hospital doors. Around them, patients and hospital personnel stop in their tracks and whip out their phones to record the strange scene.

Weaving his way through the hospital, McClary eventually found himself inside the hospital room where his son took his last breath.

“It’s just emotional,” he said, before shaking hands and exchanging hugs with the medical staff he had grown to know so well over the past year. “I needed to face this. I needed to face it,” he said, his helmet now removed, allowing his tears to fall freely.

“But we’ve got some kids to see. Let’s cheer up the kids,” he continued, putting his helmet back on.

Journeying from room to room, bed to bed, the 501st members visited sick child after sick child. Darth Vader and his Storm Troopers took turns fist-bumping one young boy wearing a white surgical mask in bed. Down the hall, a teenager posed with the cast of characters. Around the corner, another child gleefully took Kylo Ren’s lightsaber and stared at the red sword in amazement, swinging it haphazardly back and forth.

In between stops, McClary removed his helmet to catch his breath. The costumes, usually handmade by their owners, can get extremely hot inside. “Like the planet Tatooine in summertime,” the 501st’s website advertises.

McClary took his time moving through the hospital, stopping to see other children who are fighting their own cancer battles -- children his own son has gotten to know and befriend while waiting for a bone marrow match.

McClary said his son spent months waiting for a bone marrow donation, which could be attributed to his ethnic background -- his mother is Latina and McClary is white.

According to the national bone marrow registry Be The Match, a white adult has a 77% chance of finding a bone marrow match on the registry. That number falls to 41% for an Asian patient and even further to 23% for an African American patient.

This unfortunate fact is just one more reason McClary continues his work with the 501st -- to shed some much-needed attention to an unknown plight of bone marrow donation. McClary said most people don’t realize how easy it is to register (literally a Q-tip swabbed in the mouth and sent to Be The Match via snail mail) and how much simpler it is to donate now than in years past -- a process that is similar to donating plasma, an outpatient procedure.

“It only takes a few hours out of your life, but you could save some kid’s life … it literally means life and death for people,” said McClary, who has set up the "Caring Like Nicholas Foundation" to help carry out his mission of educating the public.

“We’ve got a message that we’ve got to get out, so that’s kind of what’s driving me," he added. "My way of healing is helping other people."