AURORA, Colo. (AP) — Police asked the public for help Tuesday in finding two vehicles believed to have been involved in a drive-by shooting in a park near a suburban Denver high school that left six teenagers wounded.

The victims in Monday’s shooting, boys and girls ranging in age from 14 to 18, were all expected to survive but police Chief Vanessa Wilson said Tuesday that two of them had “significant” injuries and faced a long recovery.

They are all students at Aurora Central High School in Aurora, a city east of Denver.

Numerous shell casings fired from different guns were found at the scene, and it is possible some rounds were fired by someone on foot, police said.

Officers who responded to the shooting applied tourniquets to at least two of the wounded students, police said.

Student Aariah McClain, 15, said she heard gunfire as she was walking near the school’s football field during lunch. She heard four shots at first, so she started walking toward the school. Then she heard “a whole lot more,” she said.

After the shooting, Wilson said everyone needed to be “outraged” by what happened and come forward with any information they might have to help police find those responsible.