Eric Matthew Frein admitted to Pennsylvania State Police shortly after his capture last month that he shot two state troopers because he wanted to "wake people up, because it was all he could do" (to effect government change), state police said Thursday in filing two counts of terrorism against the 31-year-old man.

The alleged confession marks the first time any concrete idea of Frein's motivation has emerged, reports the Scranton Times-Tribune. A letter state police say Frein typed to his parents and stored on a thumb drive nearly a year before killing Cpl. Bryon K. Dickson II expands on his idea that there is no one worth voting for and only a revolution could re-establish liberties Frein believes are lost. The thumb drive was found in an airport hangar where a U.S. Marshals Service team captured Frein.

Prosecutors also dropped one count of attempted homicide of a law enforcement officer Thursday. Initially, Frein was charged with two counts of the crime. The remaining count reflects the attempt on Trooper Alex T. Douglass' life. Trooper Douglass is in a New York City hospital awaiting more surgery.

Frein is the sole suspect in the Sept. 12 ambush at the Blooming Grove barracks that killed Cpl. Dickson, of Dunmore, and wounded Trooper Douglass, of Olyphant.

Both counts of terrorism are first-degree felonies and each carry a maximum penalty of 40 years in prison. Pike County District Attorney Ray Tonkin has said he will seek the death penalty.