Authorities have added terrorism charges against a man accused of ambushing a Pennsylvania State Police barracks and killing a trooper. They say he told them he wanted to "wake people up."

State police say Eric Frein (freen) called the Sept. 12 slaying of Cpl. Bryon Dickson an "assassination" in an interview after his capture.

Police filed the additional counts on Thursday. He was already charged with first-degree murder. Prosecutors are seeking the death penalty.

In court papers, police say they found a letter addressed to "Mom and Dad" on a thumb drive belonging to Frein. They quote the letter as saying that only a revolution "can get us back the liberties we once had."

A defense attorney says police refused to tell Frein his family had hired an attorney for him the night he was captured.