Law enforcement officials searching for 31-year-old Eric Frein found an AK-47-style rifle and ammunition they believe belong to the suspected police killer, according to state police.

Lt. Col. George Bivens displayed pictures of the items during a press briefing Sunday afternoon, when he said it is only a matter of time until Frein, accused of fatally shooting Cpl. Bryon Dickson and wounding trooper Alex Douglass on Sept. 12, is captured.The manhunt is currently centered on a several-square-mile area on the border of Pike and Monroe counties, near the Canadensis home of Frein's parents.“We have every reason to believe he is in the general area,” Bivens said on Sunday. “That is based on everything we are getting from our trackers, both humans and dogs. There is no doubt we are pushing him hard.”According to estimate by Bivens, Frein has traveled around 15-20 miles from the area a Jeep registered to his parents was found submerged in a heavily wooded area nearly two miles from the Blooming Grove state police barracks where the shootings occurred.While police haven't found a connection between Frein and the victims, they do believe he has a grudge against law enforcement, specifically the state police.The ambush, Bivens said, was no spontaneous act.'Frein planned this for months and maybe years,” he said. “We have reason to believe he had done surveillance on the station. He made preparations to get him ready for the attack and for his escape.”Residents in and around Canadensis spent Friday night and well into Saturday under a shelter-in-place restriction as armed officers and special agents swarmed about, giving the indication they might be close to Frein.Multiple residents reported hearing shots fired on Friday night.“We have not exchanged gunfire with Frein,” Bivens said. I am aware of the report of gunfire, but can't confirm that was even related to this investigation. We believe he is close, but we have had no opportunity to apprehend him yet.”Police believe Frein is on the move as they push him, but the rugged terrain makes it hard to quickly cover ground.“It is not an easy place to search with the dense underbrush, water and caves that are out there,” Bivens said. “It takes time to search the area with some level of safety.”The shelter-in-place restriction was lifted Saturday night as police said they try to “balance the concern of disrupting people's lives with keeping them safe.”Residents are still asked to take caution and report anything suspicious such as doors or windows that look to be forced open.“Keep your doors locked and the outside of your residences well lit,” Bivens advised.Frein, police believe, is traveling on foot and is still considered armed and dangerous.Bivens said there was no evidence to suggest he has contacted his family since the incident.Despite the amount of time that has passed since the incident, police do not intend to reduce the amount of manpower used in the search.“We are going to stay focused and the Federal Bureau of Investigation (FBI) has ensured us they are going to stay focused until an arrest is made,” Bivens said.The reward for information leading to Frein's capture is up to $175,000, but police said they haven't encountered any “bounty hunters,” an activity they described as “highly discouraged.”Several school districts in the Poconos were closed through the end of last week as the search intensified.Bivens said those decisions remain up to the individual districts.“They are going to make decisions based on what is going on in their area,” Bivens said. “We are communicating with them to help them make the best decision.”