Pennsylvania authorities have found a letter which appears to be handwritten by alleged cop-killer Eric Frein while the hunt for him continues, reports stated Monday.

The letter from the man who gunned down two Pennsylvania State Police troopers on September 12 indicated details about the ambush and his escape, as authorities continue to pursue him since he was identified last month.

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According to reports, Eric Matthew Frein himself wrote the note which did not offer any indication of a motive for the ambush.

The 31-year-old self-taught survivalist has been on the run since the attack that killed 38-year-old Corporal Bryon Dickson and gravely wounded 31-year-old Trooper Alex Douglass during an evening shift change at a state police barracks in Blooming Grove.

First reported by CNN, the Pennsylvania State Police refused to confirm the authenticity of the letter that was purportedly revealed by two unnamed reinforcement sources.

"I understand some networks are reporting information obtained through sources. This is the only official source and I cannot confirm anything reported by 'sources,'" Trooper Tom Kelly, spokesperson from the state police, said in an email to Reuters.

The initial report from CNN was also unclear when and why the note was written and whether it had been left by accident or intentionally.

The manhunt for Frein, who was known to have a grudge against law enforcement, continues as they focus on an area along the county borders of Monroe and Pike in east Pennsylvania where Frein was last reported to be hiding.

On Friday, police reported that they had located a campsite, complete with remains from supplies such as food, ammunition, and clothing, that was believed to be the suspect's latest hiding place.

They also found two 'fully functional' pipe bombs, an AK-47, soiled diapers and some Serbian cigarettes during the search.

Frein, who is now included in the FBI's Top 10 Most Wanted list, has been described by those who knew him to be "goofy but dark," with one citing that he seemed to have imitated the movie character 'Rambo' when he opened fire on the troopers. 

TagsEric Frein, Pennsylvania, ambush, cop killer, frein letter