In this context, someone who can make the woods their home and live off the land.
Not a "prepper" in this context.
There's no evidence from the article that he actually fits that description.
From the article: "Frein... lived about 20 miles from the ambush site and lived with his parents until a few months ago."
Dude is 31 and still living with mommy. Hell, he couldn't even survive in his own apartment.
Who walks their dog in the woods 2 miles from a deadly ambush of police when the suspect is still at large?