Authorities said they believe the student was armed with a firearm when he was stopped Thursday morning trying to enter Roosevelt Elementary School in Kenosha.

“A tragedy was prevented today,” Kenosha Police Chief Patrick Patton said at a news conference Thursday afternoon.

The boy in custody, who police said attended Mahone Middle School, was a former Roosevelt Elementary student. He was captured Thursday during a community-wide search in the 6700 block of 30th Street around 2:05 p.m.

“We will not be releasing the name of the individual involved at this time,” Patton said.

Kenosha Police had said they were looking for a “suspicious individual” who authorities said attempted to enter Roosevelt Elementary School from a secure area at 9:02 a.m.

The individual was reportedly carrying a backpack and duffel bag when he was stopped and questioned by school staff at the secure entrance of the building. He then ran away from the building towards the neighbourhood.

A “safe lockdown” was implemented at all Kenosha Unified schools for the remainder of the day. The Kenosha County Sheriff’s Department and Pleasant Prairie Police stationed teams at all KUSD schools, including Somers and Pleasant Prairie, and teams patrolled during the search.

Patton later said a separate report of a possible “active shooter” at Gateway Technical College in Kenosha was “unfounded” and likely resulted from the reaction of people who reported hearing about the KUSD incident.

He said a Kenosha Police Department officer was injured in a vehicle crash that occurred while units were responding to the Gateway report. The police officer was taken to hospital and is reported to be in stable condition and recovering.

In a statement released late Thursday, State Superintendent Jill Underly thanked school staff for preventing the boy from entering the building.

“Their quick action protected the students and ensured no one was injured,” he said. “The threat of violence in our schools is real and staff must prepare every day. The staff, led by Superintendent (Jeffrey) Weiss, was well trained; they saved lives today.”