Potential suspects have been detained, Sgt. Paul Parizek said, but no charges have been filed as police continue their investigation.
The teens were shot on the grounds of East High School, though not within the school building, with the gunfire apparently coming from a passing vehicle, police said.
A 15-year-old boy who did not attend the school died and two female students, aged 16 and 18, were in critical condition, police said Monday night.
“Des Moines Police Department detectives continue to investigate this incident. Witnesses are being interviewed, evidence examined, investigative leads followed, and multiple search warrants are being executed,” Parizek said.
Police said they started receiving multiple calls reporting gunfire at the school at 2:48 p.m. and found the three victims outside when they arrived. All three were rushed to area hospitals.
“I was just sitting in my friend’s car and then all of the sudden I heard 11 gunshots and some boys screaming,” Shannon said.
Shooting is ‘everyone’s worst nightmare’
“The DMPS grief team will be available at East High for students and staff beginning tomorrow through the remainder of the week. School counselors will be available at our other schools for students who need additional support,” the district said in a news release.
“I think we can all agree an event like this is everyone’s worst nightmare. Tonight, hug your students and love them,” Principal Jill Versteeg said in the statement.
Shootings in and near schools have become too common, Superintendent Thomas Ahart said.
“Our staff and students are forced to train for these incidents and the trauma associated with the repeated drills and incidents will remain with them for years to come. It’s unfortunate that our state and our country have become a place where firearms are far too easily accessible. We remain committed to protecting our students and staff, but real change to gun laws and access would go a long way to help us,” Ahart said in the statement.
Other agencies assisting with the investigation include the Iowa State Patrol, Polk County Sheriff’s Office, the FBI and the Des Moines Public Schools Department of Public Safety.
CNN’s Amir Vera, Joe Sutton and Jenn Selva contributed to this report.