He's eluded authorities for more than five years, a mountain man who roams the wilderness of southern Utah, breaking into remote cabins in winter, living in luxury off hot food, alcohol and coffee before stealing provisions and vanishing into the woods.
Investigators have clawed for clues, scouring cabins for fingerprints that match no one and chasing reports of brief encounters only to come up short, always a step behind the mysterious recluse.
They've found abandoned camps, dozens of guns, high-end outdoor gear stolen from the homes and trash strewn around the forest floor.
Authorities say the man is armed and dangerous and responsible for more than two dozen burglaries. He has continued to outrun the law across a swath of mountains not far from Zion National Park. He's roamed across 1,000 square miles of rugged wilderness where snow can pile 10 feet deep in winter.
And while there have been no violent confrontations, detectives say he's a time bomb. Lately he has been leaving the cabins in disarray and riddled with bullets after defacing religious icons, and a recent note left behind in one cabin warned, "Get off my mountain."
"You wouldn't want to come across that guy," said Iron County detective Jody Edwards, who has been working the case since 2007.
Theories about his identity have ranged from a 42-year-old man on the FBI's Most Wanted List sought for the 2004 killing of an armored-truck guard in Phoenix to a castaway from the nearby compounds of the Fundamentalist Church of Jesus Christ of Latter-Day Saints, the polygamous sect run by jailed leader Warren Jeffs.
The FBI recently discounted the theory that the man was their fugitive after authorities got the first pictures of him from a motion-triggered surveillance camera outside a cabin showing a sandy-haired man in camouflage on snowshoes, a rifle slung over his shoulder. The photos were captured sometime in December.
"We believe that is not Jason Derek Brown," FBI special agent Manuel Johnson told The Associated Press.
However, Edwards isn't so quick to rule out the possibility, given the close resemblance to Brown, who was raised Mormon and is a highly educated, well-traveled avid outdoorsman.
So while detectives believe they are getting close, buoyed by the recent photos, the shadowy survivalist remains an enigma. No missing-person report appears to fit, and fingerprints lifted from cabins have yielded no match.
Meanwhile, cabin owners are growing more frightened by the day and are left wondering who might be sleeping in their beds this winter.
"He's scaring the daylights out of cabin owners. Now everyone's packing guns," said Jud Hendrickson, a 62-year-old mortgage adviser from nearby St. George who keeps a trailer in the area.
In November 2010, Bruce Stucki, another cabin owner, said a burglar broke into his cabin through a narrow window, pried open a gun case with a crowbar and laid out the weapons but took none. At a nearby cabin, the man reportedly took only the grips from gun handles.
"He could stand in the trees and pop you off and no one would know who killed you," Stucki said.
Some cabins he has left tidy and clean, while others he has practically destroyed, even defecating in one in a pan on the floor.
"He should know he's being followed, but I don't think this guy is normal in any way," said Stucki, who, like many cabin owners, has a lot of his own theories.
"He's anti-religious, waiting for the mothership to come in," Stucki speculated.
Investigators say they have found several of the man's unattended summer camps, what they initially thought were left behind by "doomsday" believers preparing for some sort of apocalypse because of the remote locations and supplies like weapons, radios, batteries, dehydrated food and camping gear.
Edwards said two camps found a few years ago were stocked with 19 guns. One of the camps also had a copy of Jon Krakauer's Into the Wild, a book about a young man who died after wandering into the Alaskan wilderness to live alone off the land.
The cabin burglar has managed to avoid being seen all but twice over the years, each time retreating into the forest.
The coffee and alcohol the survivalist favors play into some cabin owners' assessment that he could be a castaway from the nearby twin towns of Hildale or Colorado City on the Utah-Arizona border. The so-called lost boys are said to be regularly booted from the polygamous sect there by elders looking to increase their marriage opportunities with young women.
Unlike members of The Church of Jesus Christ of Latter-day Saints, which discourages consumption of alcohol and coffee, many of the Mormon fundamentalists imbibe.
Detectives aren't sharing their latest assessments, but "we've got a lot of leads" from the surveillance photos, Edwards said. "I would say we're very close to making a positive ID on him. We just got to catch this guy."
To cabin owners in southern Utah, he remains a spooky and menacing figure.
"We feel like we're being subject to terrorism by this guy," Hendrickson said. "My wife says flat out she's not going back to our trailer until they catch him."