Investigators describe Eric Frein as a survivalist, someone with a deep hatred of law enforcement and a member of a paramilitary group.
Family and friends say Frein is a quiet person who loves war reenactments.
"It's shocking when somebody that you've been in contact with through journalism or film making does such a heinous crime," said Patrick Bresnan of Texas.
Bresnan and his wife made a documentary called "Vietnam Appreciation Day," in which Frein appeared.
The film is being test-screened now and features war reenactors.
In a phone interview with Newswatch 16's Sarah Buynovsky, Bresnan described Frein as an extremist, someone the fringe, and a "ticking time bomb" who could lose himself in the fantasy world of reenactments.
"For Eric, it was almost like a fetish. He took the weaponry very seriously. He took his uniform and the insignias and the labels that were on it very seriously," Bresnan said. "He and the people he associated with at these events were from the Pocono region and they kind of kept to themselves."
As the manhunt for Frein continues in northeastern Pennsylvania, Bresnan said he and his family are watching closely from their home in Texas.
"I really hope they find this guy. It's very scary. It's no joke."