CHICAGO (CBS) — More details emerged Thursday about the traumatic moments inside an Old Irving Park music school, where a police officer and a teenage boy were wounded in a gun battle.

As CBS 2 Investigator Megan Hickey reported, a group of young music students managed to take over.

Police said Christopher Terrell Willis, 32, led officers from multiple jurisdictions on a chase in a stolen Buick after robbing a bank in Des Plaines. Willis got off the Kennedy Expressway at Irving Park Road, where he shot and wounded a Chicago Police officer, police said.

Willis then stormed into the UpBeat Music & Arts school at 4318 W. Irving Park Rd., and Des Plaines police followed him in and shot and killed him – but also accidentally wounded a 15-year-old boy who was interning at the school.

A TIMELINE: From Bank Robbery In Des Plaines To Melee Of Gunfire In Old Irving Park

That boy and the other kids inside the music school ran out through an alley. The rest of the music students made it into the nearby Berman Subaru dealership, but witnesses said the boy who was shot didn’t get that far.

“Right in the grass up against the curb, laying down here, holding his abdomen,” said dealership employee Dan D’Andrea.

Dealership employees found the boy with a bullet lodged in his chest. Meanwhile, the group of about 10 kids, teachers, and a parent watched it unfold.

“They were running around over here,” D’Andrea said.

And they were forced to run toward safety.

“The teachers and the parents, like, you’ve got brave children,” said dealership employee Theresa Losuriello.

Losuriello and D’Andrea brought the group inside the showroom. They said some looked as young as 10. Some were crying, and some sat in stunned silence.

Losuriello turned on the TV and brought them food.

“Tried to drown out the sound that was going on outside with all the sirens and all the lights that were reflecting against the glass – the blue and red and the helicopters,” she said. “It was very chaotic.”

At last check, both the Chicago Police officer and the teen were in stabilized conditions and slowly improving.

But the music school turned crime scene remained closed on Thursday.

On the door, a handwritten message reading, “Don’t let the future stand in the way of your dream,” is taped to a piece of Beethoven sheet music. It’s the only sign that something must have happened there.

But the witnesses from Tuesday night said they’ll remember for a long time.

“The most heartbreaking thing for me was, without a doubt, the kids getting picked up,” D’Andrea said. “With the kids being held by their parents and the looks on their faces, I’ll never forget it.”

Police said Willis had an accomplice in the initial robbery of the Bank of America branch on Oakton Street in Des Plaines that started everything. That accomplice was taken into custody on Tuesday.

On Thursday night, the U.S. Attorney’s office said no charges have been filed against that suspect. We’ll keep following up.

Megan Hickey