The 20-pound spiked boulder was rigged to swing at head-level with just a trip of a thin wire _ a military-like booby trap set on a popular Utah canyon trail.
Any unsuspecting hiker exploring the makeshift dead-wood shelter could have fallen prey.
Two men arrested over the weekend on suspicion of misdemeanor reckless endangerment told authorities the traps were intended for wildlife, but investigators don't believe the story.
"This is a shelter put together by people, visited by people _ anything that would be impacted by their device would have to be humans," Utah County sheriff's Sgt. Spencer Cannon said. "It took some time to build these traps. They took rope, heavy-duty fishing line, and they intended what the traps were going to do."
U.S. Forest Service Officer James Schoeffler came across the trip wires last week while on routine patrol on the popular Big Springs hiking trail in Provo Canyon about 50 miles south of Salt Lake City. Having had previous military hazardous device detection training, Schoeffler immediately knew it was a threat. If not disabled, both devices _ one set to swing down at head-level, the other designed to trip a passer-by into a bed of sharpened wooden stakes _ could have been deadly.
The structure built by the two suspects was easy to see, Cannon said, but the booby traps could have been overlooked by everyone except a military-trained officer like Schoeffler.
"A lot of people go up there after dark, as well," Cannon said. "We're very, very fortunate that it was Officer Schoeffler who found it."
The U.S. Forest Service has not made Schoeffler available for an interview. Authorities said he disabled the traps after taking photos and video of the site.
Cannon said the traps were just a half-mile from a busy trailhead.
"Who goes up this trail thinking, I'm going to have to look out for booby traps?" he said. "A kid could say, `Oh cool, a shelter,' and run right across the trip line."
Days after Schoeffler made the discovery, a tipster alerted authorities about comments on Facebook that mentioned the traps and the shelter. Detectives then tracked down the suspects, Cannon said.
Benjamin Steven Rutkowski, 19, of Orem and Kai Matthew Christensen, 21, of Provo were booked in the Utah County Jail on Saturday and released on bail.
Prosecutors believed the misdemeanor reckless endangerment allegations were the strongest claims they could pursue without anyone being injured. Charges have not yet been filed.
Rutkowski's father, Steven, declined comment. No phone number was listed for Christensen, and it wasn't immediately clear if either suspect had an attorney.
Associated Press writer Brian Skoloff contributed to this report.