An intensive manhunt is under way for an "extremely dangerous" man who expressed the desire to kill police in the past, state police said in a Pike County news conference on the Friday state police shootings.

Eric Frein

Charges were filed against Eric Matthew Frein, 31, of Monroe County, who is believed to be the sole shooter, said State Police Commissioners Frank Noonan said.

He is accused of killing Cpl. Bryon Dickson, 38, and critically wounded another trooper in an ambush at the remote Blooming Grove, Pike County state police barracks.

Frein is described as a survivalist who has expressed anti-government leanings in past, especially against law enforcement, Noonan said.

Frein was charged Tuesday with first-degree murder, homicide of a law enforcement officer and other offenses.

In a search executed at his home, police found spent bullet casings of the type used in the shooting. Anyone with information is asked to call state police at 866-326-7256.

Noonan says about 200 law enforcement officials are looking for Frein, but his whereabouts are unknown.

The Associated Press contributed to this report, which has been updated.