BLOOMING GROVE, Pa. (AP) — Hundreds of law enforcement officers fanned out across the dense northeastern Pennsylvania woods Tuesday as they tracked a survivalist with two high-powered rifles and a grudge against police, identified as the gunman who killed one trooper and injured another in a late-night ambush outside a state police barracks.

Eric Matthew Frein, 31, of Canadensis, is "extremely dangerous" and residents in the area should be alert and cautious, State Police Commissioner Frank Noonan said at a news conference in which he revealed the suspect's name.

"He has made statements about wanting to kill law enforcement officers and also to commit mass acts of murder," Noonan said. "What his reasons are, we don't know. But he has very strong feelings about law enforcement and seems to be very angry with a lot of things that go on in our society."

Frein was charged Tuesday with first-degree murder, homicide of a law enforcement officer and other offenses. About 200 law enforcement officials were combing the rural area of northeastern Pennsylvania marked by dense forest, but "we have no idea where he is," Noonan said.

The gunman killed Cpl. Bryon Dickson, 38, and critically wounded Trooper Alex Douglass outside the barracks during a Friday night shift change, then slipped away.

Authorities were led to Frein after a resident who was walking his dog in a wooded area two miles from the barracks Monday spotted a 2001 Jeep lightly submerged in a pond and called 911. Police found shell casings inside the vehicle that matched those found at the shooting scene, Noonan said.

Investigators also found Frein's Social Security card, a Pennsylvania Game Commission range permit, camouflage face paint, a black hooded sweatshirt, two empty rifle cases and military gear, Noonan said.

Frein has held anti-law enforcement views for many years and has expressed them both online and to people who knew him, said Lt. Col. George Bivens.

"This was not unexpected," Bivens said. "As we've interviewed a number of people, that's been the common theme. This was not a surprise."

Frein's father, Michael Frein, a retired major in the U.S. Army with 28 years of service, told police that his son is an excellent marksman who "doesn't miss," according to a police affidavit released Tuesday.

Three state police patrol cars were parked at Frein's parents' home, a well-kept two-story in a private community. Several other cars were in the driveway Tuesday afternoon.

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Rubinkam reported from northeastern Pennsylvania.