'I was just shot in my school,' boy who survived deadly attack told 911: 'It's burning... my leg's going numb'

A teen who survived a shooting at his Maryland high school called 911 himself, saying, "I was just shot in my school."

"I'm sorry?" the dispatcher replied.

"I was just shot at my school," 14-year-old Desmond Barnes repeated.

A Great Mills High School teacher told the dispatcher, "He’s laying on the floor. He’s in pain,"

Desmond later took the phone back and the deputy told him, "I need you to stay calm. We have help coming to you, okay? Where is your injury?"

"In like, the back of my thigh," Desmond responded. "It’s burning. ... Oh, my knee hurts so bad."

"We’re getting help to you Desmond, OK? You need to stay strong with me, buddy," the dispatcher said. "I’m going to stay right here with you, okay? We are getting help."

"My leg’s going numb," Desmond said.

Just before 8 a.m. on March 20, the suspected shooter, 17-year-old Austin Rollins, approached 16-year-old Jaelynn Willey in a hallway and shot her once in the head, the St. Mary's County Sheriff's Office said.

The single discharged round struck Desmond in the leg, the sheriff's office said. Desmond went to a classroom for shelter and was later found by responding officers, the sheriff's office said.

Another 911 caller told a dispatcher, "There's a girl outside my door bleeding on the ground."

The caller said one shot was fired, apparently to the girl's head, and there was a pool of blood surrounding her.

After Rollins allegedly shot the two teenagers, he continued walking and was confronted by school resource officer deputy Blaine Gaskill.

Rollins fired one fatal shot to his own head, and at the same time, Gaskill fired one non-fatal shot, hitting the gun in Rollins' hand, the sheriff's office said.

Desmond was hospitalized and then released on March 21.

Two days after the shooting, Willey's mother announced her daughter would be taken off life support. The teen died that night.

Willey and Rollins "had a prior relationship which recently ended," the sheriff's office said. "All indications suggest the shooting was not a random act of violence."

St. Mary’s County Sheriff Tim Cameron called the shooting "our worst nightmare."

"This is what we prepare for," he said. "And this is what we pray we never have to do."

ABC News' Becky Perlow and Rachel Humphries contributed to this report.