DES MOINES, Iowa — Authorities arrested six teenagers, including a 14-year-old, in a shooting outside a school that killed a 15-year-old boy and seriously wounded two teenage girls, Des Moines police said Tuesday.

The suspects are each charged with first-degree murder and two counts of attempted murder in the Monday afternoon shooting on the grounds of East High School, near Des Moines’ downtown, about a half-mile from the Capitol. Police said gunshots fired outside the school came from several shooters from multiple vehicles.

Police named the suspects as Octavio Lopez, 17; Henry Valladares-Amaya, 17; Manuel Buezo, 16; Romero Perdomo, 16; Alex Perdomo, 15; and Nyang Chamdual, 14. All are from Des Moines.

Police said in a Facebook post that the 15-year-old killed, who was not a student at the school, was the intended target of the drive-by shooting. The other two shot were females aged 16 and 18, who both attend East, and were simply bystanders caught in the shooting, police said. Police had not released the victims’ names by Tuesday morning.

Police investigate a shooting outside East High School in Des Moines, Iowa, on Monday. Zach Boyden-Holmes/The Des Moines Register via Associated Press

Police said the 16-year-old girl remained hospitalized Tuesday in serious condition, while the 18-year-old remained hospitalized in critical condition.

“While this incident occurred outside of a school, it could have occurred in any one of our neighborhoods,” police said. “The school is where the suspects found their target.”

Police said search warrants were conducted at five Des Moines homes and six vehicles in the hours after the shooting. Investigators seized six guns during those searches, police said.

On the day of the shooting, calls started pouring in around 2:50 p.m. Monday, shortly before classes were scheduled to dismiss for the day, police spokesman, Sgt. Paul Parizek said.

The district said in a statement that the school was immediately put into lockdown and students were kept inside while police investigated. They were dismissed around 3:30 p.m. after law enforcement gave an all clear.

Principal Jill Versteeg described what happened as “everyone’s worst nightmare” and urged parents to “hug your students and love them.”

Officials had already suspended classes districtwide Tuesday so juniors could take the ACT college admissions test. The ACT exams and parent-teacher conferences were canceled Tuesday at East High School. The district also was making grief counselors available.

Superintendent Thomas Ahart said school shootings have “become too common” and said that “real change to gun laws and access would go a long way to help us.”

“Our staff and students,” he said, “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.”

Police said they do not believe there is a continued threat to the public. A motive was not immediately known. Authorities have recovered shell casings from the scene as they investigate what happened.

Des Moines Police Chief Dana Wingert went to the school after the shooting and expressed frustration at the violence.

“Unfortunately what happened here today was just another pointless tragedy in our community,” Wingert told TV station WOI-TV. “People using firearms to settle their differences.”

Police said it was the fourth homicide in Des Moines this year.

This report includes contributions from Margery A. Beck, reporting from Omaha, Nebraska. Hollingsworth reported from Mission, Kansas.