Suspected Upton Bomb Maker Could Get Quadruple Prison Time As Feds Take Case

The potential penalty for an Upton man accused of trying to detonate a homemade propane bomb on a drilling yard has quadrupled after his case switched from state to federal.

David Riggle, 40, is scheduled for a Friday hearing in the Casper-based U.S. District Court for Wyoming to determine if he should be in jail during his prosecution.

The U.S. Attorney’s Office charged him last week with attempting “malicious damage” to a property with fire, a felony punishable by between five and 20 years in prison and up to $250,000 in fines.

He was originally charged in Weston County on Dec. 13, with possessing or making explosives. That’s a state charge punishable by up to five years in prison and $5,000 in fines.

But Weston County Attorney Michael Stulken in a motion filed Wednesday asked the Weston County District Court to dismiss that case. Stulken’s motion doesn’t reference the federal case, but it followed the federal case’s April 23 filing by less than a week.

Riggle’s attorney, Joshua Taylor, did not immediately respond to a Thursday request for comment.

Propane Tank

Someone at the Tyvo drilling yard one mile south of Highway 116 just outside Upton, Wyoming, contacted the Weston County Sheriff’s Office the morning of Nov. 30, says an evidentiary affidavit by Deputy Jared Engle.

The yard owner said one of his drilling rigs broke down, so he called in a maintenance man the night of Nov. 29 to get the rig running. The maintenance man realized the replacement part he needed may be in a storage trailer on the yard. He got the part he needed and headed for home at about 5:30 p.m., says the affidavit.

But the maintenance man forgot his flashlight.

He went back into the storage trailer the next morning to retrieve the flashlight and smelled propane, the document says.

Inside the trailer the man noticed the 100-pound propane tank’s valve turned open — and an ignition device off to its left, says the affidavit.

The man opened the trailer’s big front door to let the propane gas out and called the yard owner.

A Look About

Engle went into the trailer to look around and noticed a 6-volt, ELECTRYX brand battery with two wires coming from it — one strung to an egg timer and fastened with glue, and another wound around a small piece of what looked like fireworks fuse, the deputy wrote.

“When the egg timer hit zero it would connect the two ends of the wire that have been soldered,” he added.

Engle called the Campbell County bomb squad, which was on scene by 10:39 a.m., the deputy noted.

The battery appeared to have heated but there was no evidence of a burn to the wires or fuse, says the document. The bomb squad deputies searched the trailer for other devices and found none, reportedly.

Those deputies theorized that this was likely a “trial run,” and whoever made the device was going to try again until he or she succeeded.

Engle noted in the affidavit that he asked the drilling yard owner if anyone had a problem or vendetta against him at that time, and the man said no.

Who Sells This Thing?

Weston County investigators canvassed nearby areas for vendors that sold that model of battery.

The local Bomgaars store in Newcastle kept that battery, but had only sold one two-pack — on Nov. 25 just after midday, says another affidavit filed in federal court by Brett Claflin, special agent of the U.S. Bureau of Alcohol, Tobacco, Firearm and Explosives.

The buyer paid $21 in cash for the $20.81 battery set, says the federal affidavit.

Bomgaars’ surveillance footage showed a person wearing a black stocking cap, a black sweatshirt with a square logo on the left chest area and writing on the left sleeve, and black or grey pants.

Searching nearby stores, investigators found a nearby Maverik gas station had video of a person who looked the same. In Maverik’s clearer video, the square logo looked like a John Deere logo, says the affidavit, which also includes video still photographs.

The Maverik video captured an image of that person’s vehicle, a Suzuki SUV, says Engle’s affidavit.

But Engle couldn’t see the license plate. It was covered with dirt, he wrote.

Weston County Sheriff Brian Colvard told Engle the ATF would be in Newcastle soon to help with the investigation.

“And we all were glad,” wrote Engle, that they’d been able to identify the vehicle before the ATF’s man arrived.

A Chance Encounter

Colvard happened to be at the Newcastle airport delivering paperwork Dec. 4 when he spotted the Suzuki SUV his personnel were all seeking, the document says.

Engle was back at the office waiting for Claflin.

Colvard radioed in the vehicle’s location to a sergeant, who was able to read the plate number and trace it back to Riggle, the affidavit says.

Riggle’s listed address was near the drilling yard where investigators had found the battery, Engle noted.

Man Trackers

Engle contacted Lynn Busskohl, an apprentice-level man-tracker who also serves Weston County Search and Rescue.

Busskohl found tracks leading from the drilling yard back to Riggle’s property, says the document.

Claflin felt he had enough to get a search warrant for Riggle’s home, the deputy added.

Brian Zerbe and Terry Browder, “top level” man-trackers, joined the investigation and observed boot tracks inside the drilling yard storage trailer.

Law enforcement executed search warrants Dec. 11, during which deputies put Riggle in investigative detention.

Riggle without being asked told Claflin during an interview that his phone quit working, so he was using an egg timer in the shed to know how long he’d been working — and someone stole the egg timer, wrote Engle.

The Hunt

Claflin’s affidavit describes this search in more detail.

It says agents found one 6-volt ELECTRYX battery (believed to be the other from the two-pack), safety fuse, black wires, and solder.

Claflin also wrote about his interview with Riggle.

Riggle said he had a “bunch of crap stolen out of his shed,” the agent related, and that an egg time was among the stolen things.

At some point, Riggle got into a debate with Claflin about whether a person could use a candle for lighting in a room flooded with propane, the affidavit relates.

“I’m not all too familiar with propane, but I would have to assume it has to get a proper concentration in the air before it will combust,” Riggle said, according to Claflin’s affidavit.

The document says Riggle also ventured some particulars about how easy it would be to calculate the cubic feet per minute of a propane flow.

In a later interview, Claflin wrote, Riggle described going into the yard and recalled a 100-pound propane tank being in the storage trailer.

Clair McFarland can be reached at clair@cowboystatedaily.com.