Keebler is being held in Salt Lake County jail and will have a June 29 detention hearing. He faces five to 20 years in a federal prison if convicted of the charge.
Charging documents say Keebler is the commander of a citizen militia group headquartered in Stockton. He was present at the April 2014 standoff with federal land administrators near the Bunkerville, Nev., ranch of Cliven Bundy, and he was an associate of Finicum, who was killed in late January by Oregon state police after he tried to avoid their roadblock in eastern Oregon amid an occupation of a federal wildlife refuge. The Tribune wrote about Keebler in December 2011, when he worked as an outfitter guiding coyote sport hunters.
Undercover FBI employees became members of Keebler's "Patriots Defense Force," charging documents say, and trained for an "anti-government action" where, Keebler told members, they would be "going on the offensive."
Keebler's group scouted the BLM office in the Gateway Mall in Salt Lake City as a potential target, but found it unsuitable due to the commercial and homeless activity, charging documents state.
Prosecutors allege that Keebler told the group it would target BLM facilities in "the middle of nowhere," damaging vehicles and buildings. He asked a militia member who happened to be an undercover FBI employee to build an explosive device.
In April, the militia member showed him a video of a 6-inch pipe bomb blowing up office furniture in the mountains of southern Utah. Keebler asked the militia member to make more of those bombs, saying he hoped to target a BLM cabin in Mount Trumbull, Ariz., that he had visited for reconnaissance in October 2015. (Editor's note: He was a guest of Finicum's, prosecutors later clarified at a later detention hearing, but Finicum did not accompany Keebler on the alleged scouting mission, as the charging documents state.)
He wanted two bombs one that he would detonate near one of the cabins at the Mount Trumbull facility, and the other to use against law enforcement agents if they were stopped driving to or from Mount Trumbull.
Keebler planted the device which, unknown to him, was inert late Tuesday. He tried multiple times to detonate the device remotely, charging documents state, before departing. The FBI arrested him Wednesday morning in Nephi.
According to the charging documents: "Keebler made it clear he didn't plan on blowing people up for now, but he wanted his group to be prepared to escalate things, and take people out if necessary."
West Valley City resident Pete Olson attended Keebler's initial court appearance Thursday, having met Keebler at Finicum's early-February funeral in Kanab.
Olson said he didn't know Keebler to have any involvement with explosives. Rather, Olson said, Keebler tried to educate people about what he felt was an unconstitutional use of power by the federal government.
"Bill's always been a good, friendly guy," Olson said. "Many people are upset with the current direction of the government."
A news release says the FBI's Salt Lake City Joint Terrorism Task Force led the investigation with help from the FBI in Phoenix, BLM law enforcement and local law enforcement.
Mount Trumbull is near the BLM grazing allotment owned by Finicum, known as Tuckup.
Finicum was fined $12,000 after his cattle were found last August to be grazing on the land before the permitted season. His wife, Jeanette Finicum, recently said she hasn't determined how to proceed, but the Finicum cattle were still grazing on the allotment in May, past the dates allowed by their permit. Jeanette Finicum could not immediately be reached for comment Thursday.
Mount Trumbull was also the name of a nearby town founded by Abraham Bundy Cliven Bundy's great-grandfather a Mormon settler who had left Mexico during the revolution in the early 1900s.
In 2001, the BLM worked with Bundy descendants to rebuild the town's iconic white schoolhouse after it had been destroyed by arsonists.
Editor's note: An earlier version of this story, which relied on charging documents, stated that William Keebler scouted a BLM cabin with LaVoy Finicum in October 2015. A prosecutor clarified at a June 29 detention hearing that while Keebler visited Finicum's home around the time, Finicum did not join Keebler on the alleged scouting mission.