Canadensis , Pennsylvania ( CNN ) -- The self-taught survivalist accused of killing one Pennsylvania state trooper and wounding another planned the ambush for months , police said . Authorities continue their search for suspect Eric Matthew Frein on Sunday but were yet to have cornered him in a wooded area around the Pike and Monroe county border . `` Based on our investigations , we know Frein has prepared and planned extensively for months or maybe years , '' State Police Lt. Col. George Bivens said Sunday . He planned his attack and retreat . However , we believe we are closing in on him . '' The suspect has had the advantage of knowing the terrain where he is hidden , but police say his head start is fleeting . `` Our tactical operations people now also know his backyard , the area he once felt safe in , '' Bivens said . `` We are pushing him hard , he is no longer safe there and I am confident he will be apprehended . '' Frein is being sought in the death of Cpl . Byron Dickson in a September 12 ambush outside the Pennsylvania State Police barracks in Blooming Grove . He is also suspected of wounding another officer . He is still considered armed and dangerous , and police have found several items that Frein had either abandoned or hidden , he said . An assault rifle and ammunition are among the weapons recovered , Bivens said . There have been several possible sightings of the suspect , but Bivens declined to label any as a confirmed sighting . While a shelter-in-place order for residents near the primary search area has been lifted , people should stay out of the woods where law enforcement officers are looking for the self-taught survivalist , police said . Frein is on the run and possibly armed , but there is no indication that he is a danger to anyone other than law enforcement , Bivens said . If he wanted to harm civilians , he 's had the opportunity to do so , he said . `` While we can never completely rule out an act of violence , I am convinced that Frein has engaged in a personal battle with law enforcement , specifically the Pennsylvania State Police , and will likely stay focused on that fight , '' he said . Police on Friday had surrounded an area where Frein was believed to be hiding , the chairman of Barrett Township board of supervisors , Ralph Megliola , said . He added that he was unaware if there had been any credible sightings of Frein since then . The area is not far from Frein 's family home in Canadensis , in the Poconos . There were gunshots in the area , but Bevins said they were not related to the search , and that officers and the suspect have not exchanged gunfire . As many as 400 law enforcement officers were involved in the search , including members of the U.S . Marshals Service , the Bureau of Alcohol , Tobacco , Firearms and Explosives , and the FBI . Canadensis is about 20 miles from the site where Dickson was shot . The FBI has placed Frein on its Ten Most Wanted Fugitives list and is offering a $ 100,000 reward for information leading to his arrest . Frein is a survivalist with an extensive shooting background and a grudge against law enforcement , officials have said . Frein apparently cut his hair into a mohawk style before the attack on police and was active in a military simulation unit that re-enacted Cold War-era European conflicts , officials said . His FBI most-wanted poster describes him as a `` heavy smoker , a weapons enthusiast , and a survivalist . He claims to have fought with Serbians in Africa , and he has studied Russian and Serbian languages . '' State Police Commissioner Frank Noonan said Wednesday that investigators know Frein `` has made statements about wanting to kill law enforcement officers and also to commit mass acts of murder . '' `` 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 . '' Trooper shooting suspect might try to target more officers , police say . CNN 's Chris Welch and Sonia Moghe reported from northeast Pennsylvania while Mariano Castillo reported and wrote from New York . CNN 's Steve Almasy , Ralph Ellis and Jason Carroll contributed to this report .
NEW : Police believe ambush was planned for months . NEW : Suspect 's battle appears to be with police , not civilians , authorities say . Hundreds of officers resume search hours after apparently closing in on suspect . Eric Matthew Frein , 31 , a self-taught survivalist , is wanted in state trooper 's death .