GERMANTOWN, Wis. (AP) – Police officers in suburban Milwaukee have killed a person who fired at them from a middle school roof.

Dozens of students were in the building during the exchange of gunfire but none were hurt, officials said.

The incident began around 6:30 p.m. Monday when officers with the Germantown Police Department responded to a call of a person acting “erratically” in Kennedy Middle School’s parking lot, the Wisconsin Department of Justice said in a statement. When officers arrived the person climbed onto the school’s roof and fired at them.

Three officers returned fire, killing the person, the statement said. As many as 70 students were in the school, which went into lockdown. The students were later bused to an elementary school where they were reunited with family.

“This is believed to be an isolated incident,” the Justice Department statement said, adding that there’s no danger to the public. “All interactions with the subject occurred outside of the building.”

The school district canceled all classes on Tuesday. The three officers who fired their weapons have been placed on administrative leave as per department policy.

The Justice Department is leading the investigation into the incident. The department’s spokesperson, Gillian Drummond, declined Tuesday morning to release the person’s name, gender, or age or comment on the person’s behavior or why the person came to the school.

She said she couldn’t release any further information due to the ongoing investigation, adding that agents need to interview witnesses and the officers involved.

Germantown School District Superintendent Chris Reuter posted a message on Facebook early Tuesday afternoon reiterating that the incident was an isolated event and there is no threat to school safety.

Reuter said classes would resume around the district on Wednesday except at the middle school since students won’t be able to access the building for an unknown length of time.