When a student stood in the middle of the quad at Saugus High School and opened fire, two teenagers were killed and three others were wounded.
One bullet struck 14-year-old Andrew Gardetto in the leg as the chaos unfolded last week at the Santa Clarita school. The teenager was rushed to a hospital and was released the same day.
His friend, 14-year-old Dominic Blackwell, a fellow member of the school's ROTC organization, died in the shooting.
Holding himself up on crutches and standing alongside other students at a vigil honoring the victims Sunday, the boy recounted the horrifying moments.
"The school shooter took away one of my friends. He injured me, he injured many people and he traumatized the entire school and community," Gardetto said.
The shooter fired randomly at the crowd before turning the gun on himself. It all took place in 16 seconds, Los Angeles County Sheriff Alex Villanueva said.
But Gardetto says he struggles with feeling like he could have done more in those few seconds.
"I feel a lot of guilt, because I could have helped Dominic and everyone else there. But I chose to run. I feel really guilty for that," he said.
The teenager said that day at the school started like any other, but soon turned into what he hesitates to call the worst day of his life. He said he didn't want to call it that, because he imagines it's worse for the parents who lost their children.
Gracie Anne Muehlberger, 15, was also killed in the shooting.
Two other girls, ages 14 and 15, were hospitalized for days after being wounded. One had been shot in the left shoulder and lower right abdomen, and the other below the belly button, doctors said.
"It's been a tiring few days," Gardetto said. "I"m still in pain."
The gunfire sent panicked students running out and others barricading in offices and classrooms, including some of the victims who had been shot.
Gardetto said that the trauma and adrenaline going through him helped him run, despite his wound. The boy could only feel the pain from the gunshot afterwards.
"When you realize you've been shot, your life has been changed completely," the boy said.
The suspected shooter, identified as 16-year-old Nathaniel Berhow, died at a hospital a day after the shooting, sheriff's officials said.
Investigators were still trying to determine whether the gun found at the scene is related to several other unregistered firearms found at his home.
The motive behind the shooting and where the gun came from remain under investigation.
Authorities did not find a manifesto, diary or suicide note that would identify a motive, Capt. Kent Wegener of the Sheriff's Homicide Bureau said at a news conference Friday.