DES MOINES, Iowa >> An Iowa teenager feared for his life when he fatally shot two fellow students at an alternative educational program for at-risk youth, his lawyer said Thursday, rebutting a claim by prosecutors that the shooting was a premeditated attack on rival gang members.

Preston Walls, 19, is one of two students charged in the shooting at the Starts Right Here program on Jan. 23, which killed 18-year-old Gionni Dameron and 16-year-old Rashad Carr. The victims’ families have denied they were involved in gangs.

The school’s founder Will Keeps, himself an ex-gang member, was wounded trying to intervene to stop the violence. He still has lingering injuries.

As Walls’ trial began Thursday, attorney Glen Downey said his client admits he pulled the trigger but did so because “he didn’t want to die.”

“Preston decided he didn’t want to go home to his family in a pine box,” Downey said.

Prosecutor Stephanie Cox told jurors they would hear testimony from Keeps and see footage of the shootings.

“You will watch a video and you will see with your own eyes Preston Walls shoot 30 times,” Cox said.

Walls is charged with two counts of first-degree murder, attempted murder and criminal gang participation. Jury selection had stretched for more than three days.

Bravon Tukes, 19, is set to stand trial on the same charges on Oct. 2. Police allege that Walls fired the shots before fleeing in a car driven by Tukes.

Prosecutors opened their case by playing an at-times graphic police bodycam video showing the chaotic scene when officers arrived. Jurors could see the victims lying on the school floor and watched as an officer attempted CPR on one of the teens.

Lt. Andrew Phipps described the “smell of gunpowder” when he entered the school and numerous shell casings on the floor.

YaVonne Palmer, an administrator at Starts Right Here, was down a hallway when the shooting started. She said the sound of bullets being fired created such a cacophony that she thought it sounded like a cupboard full of dishes were being smashed.

Prosecutors initially sought to try Walls and Tukes together but the judge separated the proceedings at the request of Tukes’ lawyer, who plans to seek Walls’ testimony in his client’s defense. The trial for Walls is expected to last about a week.

Police arrested Walls less than an hour after the shooting at the school on the edge of downtown Des Moines.

The alternative program, which is affiliated with the Des Moines public schools, closed immediately after the shooting but reopened within a few weeks. About 30 students now attend the program.

Keeps, the school’s founder, was a 15-year-old member of a Chicago gang when he witnessed rival members kill his friend. He escaped the streets and moved to Iowa to help other young people from troubled backgrounds.