On a nature hike, as a rule, the dangers you want to guard against are dehydration, getting lost, and bears. But of all of nature’s creatures, the most terrifying might be a duo of teenage boys without much to do. In Utah, two such young men were arrested on suspicion of setting up trap that consisted of “a 20-pound spiked boulder … rigged to swing at head-level with just a trip of a thin wire — a military-like booby trap set on a popular canyon trail,” according to the Associated Press.

Luckily, the person who found the trap recognized it, the AP reported:

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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 two men arrested claimed that it was “intended for wildlife.” Which is why they set it up near a little dead wood shelter that would have attracted a curious kid or an unsuspecting French tourist. Perhaps the Forest Service should consider issuing a new type of alert: “Teenage boys have been seen in area. Avoid direct eye contact, and back away slowly.”