Police say the hard drive of a computer used by the suspect in the deadly ambush of Pennsylvania state police troopers provides evidence he has been planning an attack for years and preparing to avoid arrest.

State Police Lt. Col. George Bivens said a police inspection of the hard drive shows Eric Frein did Internet research on how to avoid police manhunts and on law enforcement technology and survival skills.

Bivens said Frein might now be treating the dragnet in northeastern Pennsylvania as "a game — a war game, if you will."

Authorities believe they have Frein contained within a 5-square-mile perimeter around his parents' home in Canadensis. They provided new details Friday, two weeks after a gunman opened fire at the state police barracks in Blooming Grove, killing Cpl. Bryon Dickson and injuring a second trooper who remains hospitalized.

Frein has managed to elude hundreds of law enforcement officials looking for him in the thick woods around his parents' home in Canadensis, taking advantage of the difficult terrain to keep them at bay. He is believed to be armed with at least one high-powered rifle.

"I suspect he wants to have a fight with the state police, but I think that involves hiding and running since that seems to be the way he operates," Bivens said. "I expect that he'll be hiding and try to take a shot from some distance from a place of concealment, as he has done in the past."

Underscoring the danger they face as they pursue him, Bivens said Frein had experimented with explosives, citing materials that police found and interviews with people who knew him. Trackers are proceeding through the thick woods as though they are booby-trapped, he said. Police think Frein might have a radio.

A police dog picked up Frein's scent several days ago and flushed him from his hiding place. But the distance was too great, and Frein was able to get away, the dense canopy providing cover from a police helicopter overhead, Bivens said Friday.

As the search for the gunman neared its third week, Bivens said he remains confident police will catch their man — "at some point."