Authorities in Pennsylvania believe the search area for a gunman who went on a deadly ambush at a state police barracks is narrowing Monday as investigators look into reports of sightings.

State Police Lt. Col. George Bivens said authorities have received “very credible” tips on the whereabouts of Eric Frein, an FBI Ten Most Wanted fugitive charged with killing one trooper and seriously wounded another 10 days ago.

Pennsylvania Gov. Tom Corbett said at a press conference in Blooming Grove -- near the barracks -- that he's confident that Frein will be caught.

The governor also thanked the hundreds of law enforcement officials who are methodically searching the rural, rugged northeastern Pennsylvania terrain.

"They are putting their life on the line for someone who has the intended purpose of killing police officers," Corbett said.

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Investigators have said the suspect they describe as a self-taught survivalist who hates law enforcement had been planning a confrontation for months, if not years. They believe he is still armed and dangerous and possibly concealing himself in self-built bunkers.

Bivens on Sunday said authorities have discovered items that Frein hid or abandoned in the woods -- including an AK-47 assault rifle and ammunition they believe he had been carrying while on the run.

"We are pushing him hard, he is no longer safe and I am confident that he will be apprehended," Bivens said.

Authorities did not yet know if the weapon had been used in the ambush, he said. Still, police believe Frein remains dangerous and possibly armed with a .308 rifle with a scope that police say was missing from the family home along with the AK-47.

Since the Sept. 12 shooting, there have been no confirmed sightings of or contact with Frein, who was placed on the FBI's Most Wanted list after the ambush at the Blooming Grove police barracks that killed Cpl. Bryon Dickson, 38, and critically wounded Trooper Alex Douglass.

The search is focusing on a several square-mile area on the border of Pike and Monroe counties around the nearby village where Frein grew up, Bivens said.

"We know that Frein has prepared and planned extensively for months, and maybe years," Bivens said. "He planned his attack and his retreat."

Bivens said Frein initially had the advantage of knowing the rugged terrain around the area.

"Our tactical operations people now also know his backyard, the area he once felt safe in," Bivens said.

Heavily armed police and federal agents on Friday descended on the community of Canadensis where Frein, 31, had lived with his parents, ordering residents to stay inside and preventing anyone outside the neighborhood from returning to their homes. Law enforcement officers wearing bulletproof vests and armed with rifles scoured the woods as helicopters buzzed overhead.

Police ordered the lockdown, believing that Frein was close and there was the possibility of a confrontation, Bivens said. Now, they are telling residents to go about their normal lives but remain vigilant, keep their doors locked and stay out of the dense, boggy woods where the search is underway.

Bivens said police cannot "100 percent" guarantee the safety of area residents but said officers are doing their best to ensure that Frein is not in the immediate area of where most of them live.

Although Bivens declined to discuss what police believe was Frein's motive or mindset, he said they believe Frein is focused solely on attacking law enforcement, not civilians. Police are in contact with area schools that closed Thursday and Friday because of the manhunt, and it is up to them when to reopen, Bivens said.

Asked whether it was foolish for Frein's scheme to include returning to the area where he lived, Bivens replied, "I don't say that it was well-planned, I say that it's been planned."

Bivens said Frein had covered perhaps 15 or 20 miles on foot since the shooting and authorities do not believe he has contacted his family. Police have no information that he's being helped by anyone, he said.

Bivens asked residents to report any shelters or bunkers that Frein may have constructed and asked hunters to review footage from trail cameras set up to track wildlife.

The Associated Press contributed to this report.