The discovery of two powerful pipe bombs during a manhunt in the Pennsylvania woods indicates the fugitive wanted in an ambush on state troopers is stressed out and making mistakes, authorities said as they repeated a call for him to surrender.

The explosives were not deployed, but they were fully functional and capable of causing significant damage, state police Lt. Col. George Bivens said Tuesday.

Officials are convinced the weapons belonged to 31-year-old Eric Frein, a self-taught survivalist who has been on the run since Sept. 12. He's charged with killing one trooper and seriously wounding another outside their barracks in Blooming Grove.

The bombs were among several items that Bivens described as being "hastily discarded" by Frein at a campsite in the rugged terrain of the Pocono Mountains. He declined to identify the other objects but said Frein abandoned them "under pressure" from the dragnet.

Bivens then addressed the suspect directly during a news conference: "You are clearly stressed. You are making significant mistakes."

The disclosure about the bombs comes as deer hunters prepare for bow hunting season to open this weekend. Pennsylvania Game Commission spokesman Travis Lau said Wednesday that hunting and trapping on public and private lands will be banned in seven townships in the area of the search, which is teeming with hundreds of heavily armed law enforcement officers. Parts of three state game lands will be closed to the public altogether.

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The bombs' discovery prompted "more of a push for us to keep hunters out of the woods and ensure their safety, and ensure that hunters and trappers don't hinder the potential apprehension of Frein," Lau said.

Hunters have already been asked to keep an eye out for cabins or other structures that look like they've been tampered with or used by Frein.

Officers have found several structures where they think the suspect has stayed, Bivens said, and police also know what Frein is eating and drinking. He noted there had been at least one credible sighting of Frein this week - from between 75 yards and 100 yards away, and through thick woods.

This probably wasn't Frein's original getaway plan, Bivens said, although he believes the suspect "had prepared to some degree for this possibility." Frein's car was found submerged in a swamp several miles from the barracks a few days after the shooting.

"I think things went wrong with his plan," Bivens said. "I think he at least believed he would have another opportunity to prepare before he went off into the woods, and he didn't get that opportunity."

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Authorities say Frein has a vendetta against law enforcement and ambushed two troopers during a shift change. Cpl. Bryon Dickson was killed and Trooper Alex Douglass remains hospitalized with unspecified injuries. Douglass has a long road to recovery, Bivens said.

Dickson wasn't even supposed to work the night of the attack, according to Bivens, but was filling in for another trooper. He said there's no evidence to suggest Frein deliberately targeted the troopers he shot.