A Minneapolis high school was locked down after classes had ended for the day after a man who was believed to have a gun ran inside the building.

Police say a couple hundred students, staff and coaches were still in Patrick Henry High School Tuesday afternoon when a "code red" was called and classroom doors were locked and lights were turned off.

Authorities say officers were called to the school around 3:30 p.m. when a man, possibly armed, was seen by witnesses entering a side door of the building. Police said late Tuesday that the man had tried to get on a Metro Transit bus, then entered the school and left minutes later.

Police searched the school room by room. Officers escorted students out of the building. The suspect has not been found.