A man with a knife caused a stir this afternoon at the main library on the University of Arizona Campus.

Campus police received calls just before 12:30 p.m. reporting a man holding a knife was on the third floor of the library, said Sgt. Juan Alvarez, spokesman for the UA Police Department.

“People were frightened because of his behavior,” Alvarez said.

Responding officers quickly subdued the man. He was not a student at the university, Alvarez said.

A photo on Twitter purported to have been taken during the incident shows four officers — two kneeling next to the suspect on the floor of the library, one overseeing the situation and one with a gun drawn and aimed at the man.

The investigation is ongoing.

Senior Editor, News, Arizona Daily Star, Tucson, Az.