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Lt. Col. George Bivens, who is leading the manhunt, sent that message to Frein as the dragnet was almost two weeks old.
Bivens had earlier said there were indications that Frein had access to the media and today he said, "I have reason to believe he may have a radio with him." Bivens delivered a taunting message to Frein.
"You are a coward," the officer said.
"We are not intimidated. We will not leave... We will find you and we will bring you to justice."
The posse hunting Frein zeroed in on a section of Pennsylvania wilderness because the suspect turned on his cell phone in an attempt to call his parents, sources familiar with the investigation confirmed to ABC News today.
Frein's phone was only on for a few seconds, but it was long enough for investigators to track the signal to an area near the border of Monroe and Pike counties in the Pocono Mountains, the source said.
Bivens declined to discuss the cell phone call saying, "I'm not going to comment on anything that may have been done with cell phones."
The break in the manhunt, first reported by the Philadelphia Inquirer, came six days after Frein, 31, allegedly ambushed Pennsylvania state troopers at their barracks, killing one officer and critically wounding another.
As many as 1,000 officers have been scouring the woods and surrounding areas for Frein. Bivens said today that searchers have "found evidence there has been tampering with some structures in the area," and officer suspects it was the work of Frein.
The mountain dragnet sent officers to a sprawling abandoned hotel called the Buck Hill Inn near the town of Cresco. The search failed to locate Frein.
"We do know he has an interest in that location and do know he has spent some time there," the colonel said.
Bivens said that Frein has "experimented with explosives," and "We are taking that into consideration," alert for "booby traps" while checking cabins and caves where Frein might have been hiding.
The manhunt has included the use of helicopters and dogs and the combination appears to have flushed Frein out of a hiding spot earlier in the week, but he escaped into woods as it got dark, Bivens said.
"On at least one occasion.... (a tracking dog) caused him to jump out at quite some distance from us and escape," Bivens said. He said the incident occurred a few days ago "just as darkness was falling," which made it difficult for the helicopter above to spot him.
He said the last sighting of Frein was on Wednesday.
The investigators said they have recovered a hard drive from a computer that Frein had access to that included internet searches and research on how to evade a police manhunt and survivalist techniques.
Investigators are also looking for anyone who may have seen Frein's Jeep Cherokee Sport before Monday, Sept. 15 in and around the Blooming Grove station where the ambush occurred, Delaware State Forest and the White Deer recreational areas.
The vehicle was found partially submerged in a pond and inside the car were shell casings that matched the bullets fired at the troopers along with face camouflage and two empty rifle cases.
An AK-47 rifle and ammunition was later found in the woods that police believe Frein either abandoned or had stashed.
Frein is believed to be armed with a .308 rifle with a scope, police have said, and consider him to be extremely dangerous.