Terrorist attack on the FBI; The attacker escaped, the search is underway PHOTO

A driver crashed his car into the gates of the FBI office in Pittsburgh early Wednesday morning, then left "as if nothing had happened" - which the agency is treating as an "act of terrorism."

The car, scrawled with profanity, crashed into the rear entrance gate of the building on the south side of Steel City around 2.40 a.m. The driver got out of the vehicle and threw an American flag over the fence while shouting indistinctly.

Authorities said they were looking for Donald Henson, an ex-military man with a history of mental health problems.

"We are looking at this as an act of terrorism against the FBI," Assistant Special Agent in Charge Christopher Jordan said, according to CBS News.

"This was a targeted attack on this building. The car reportedly had profanity on one of the side windows, which is being investigated. The FBI said no one was injured during the incident. The bomb squad was called to the scene and a white Toyota was seen as authorities searched the car outside the gate. Henson, of Penn Hills, is being sought, and is believed to be unarmed but has a history of mental health issues," the FBI said.