BLOOMING GROVE, Pa. - A man described as a "survivalist," a trained marksman with antigovernment leanings, was the gunman who killed one state police officer and injured a second in an ambush outside the barracks here last week, investigators said Tuesday.

At an afternoon news conference, police said they identified 31-year-old Eric Matthew Frein from documents he left in a Jeep he abandoned about two miles from the barracks, where he ambushed Cpl. Bryon K. Dickson and Trooper Alex Douglass on Friday. Dickson was killed and Douglass critically injured.

Frein, who lived with his parents in Monroe County, was at large and considered extremely dangerous, possibly armed with a high-powered rifle that looks like an AK-47, police said.

Scores of officers fanned out across the region, and police scrambled to respond repeatedly to reports of shots being fired, but nothing led to Frein.

State Police Commissioner Frank Noonan said investigators believe Frein did not target Dickson and Douglass specifically, but law enforcement officers in general.

"He made statements about wanting to kill law enforcement officers and to commit mass acts of murder," Noonan said.

Investigators zeroed in on Frein on Monday after a man came across his Jeep, apparently stuck in a holding pond in a deeply wooded area in the Poconos.

Inside they found Frein's Social Security card, game permit, and other items, including face paint, spent cartridges, and information on various foreign embassies, according to an affidavit filed in the case. Police also found spent shell casings in his bedroom.

Frein's father, E. Michael Frein, is a retired Army major who served for 28 years, the affidavit said. He lives with his wife and son in Canadensis, south of Blooming Grove.

He allegedly told investigators that he had trained his son in shooting skills and that the younger Frein was a member of his high school shooting team.

According to his father, Eric Frein "doesn't miss," the affidavit said.

Police said the shooting was not a surprise to some who knew Eric Frein.

"This was not something he kept quiet," Noonan said, without elaborating.

Police said Frein, who has blue eyes, stands about 6-foot-1 and weighs about 165 pounds.

Late Tuesday, troopers stood outside Frein's parents' house in Monroe County as state police cruisers lined the gravel road. The officers declined to comment to reporters or let them approach the house.

A neighbor who asked not to be identified called Frein's parents "great people" who looked after the elderly in the neighborhood.

The woman said she had never met the younger Frein during her 13 years in the neighborhood, though she often saw him walking. He was in "perfect physical condition," she said.

"He was always off to himself," she said. "I just assumed he was extremely smart and eccentric."

Frein was charged in a warrant with first-degree murder and attempted first degree murder as well as criminal homicide of a law enforcement officer and attempted homicide of a law enforcement officer.

Dickson, 38, served at the Philadelphia barracks for a year before transferring in June to Blooming Grove, in rural Pike County. He had grown up in northeast Pennsylvania and lived with his wife and two children in Dunmore, a suburb of Scranton.

The gunman fired at the troopers from a wooded area across from the barracks as Dickson was leaving after his shift and Douglass was beginning his.

Douglass remained hospitalized Tuesday.

Dickson was the 95th trooper to die in the line of duty and the first since 2012. His Funeral Mass will be Thursday morning at St. Peter's Roman Catholic Cathedral in Scranton.

bfinley@phillynews.com 610-313-8118 @Ben_Finley