A 57-year-old Stockton man, described by prosecutors as the "commander of a citizen militia group," was federally indicted Thursday after allegedly trying to blow up a Bureau of Land Management cabin in Mount Trumbull, Ariz.

SALT LAKE CITY — A Stockton man described by prosecutors as the "commander of a citizen militia group" was indicted Thursday after allegedly trying to blow up a Bureau of Land Management cabin in Arizona.

William Keebler, 57, was indicted in U.S. District Court on one count of attempted damage to federal property by means of fire or explosive. He was arrested Wednesday in Nephi by combined forces from the FBI and BLM.

Keebler is the leader of a group called the Patriots Defense Force, according to charging documents filed in federal court. He was allegedly present for the standoff in Bunkerville, Nevada, between BLM agents and a group that included Cliven Bundy. He was also an associate of Lavoy Finicum, an Arizona rancher who participated in the takeover of the Malheur Wildlife Refuge near Burns, Oregon, and was later shot and killed by federal agents while resisting arrest, according to prosecutors.

Keebler believed "the BLM was overreaching their authority to implement grazing restrictions on ranchers" and that the "government had been allowed to harass people, but the repercussions were going to start," the charges state.

Prosecutors say undercover FBI agents became members of Keebler's Patriots Defense Force for several months. Keebler gave them military, firearms and survival training, and on May 15, 2015, talked to the undercover agents about "putting teams together and 'going on the offensive,'" the indictment states.

Keebler allegedly scouted out the BLM office in Salt Lake City near The Gateway shopping center but decided to target BLM facilities in more remote locations. He then decided on the BLM facility in Mount Trumbull, Arizona, police say.

He had one of the undercover agents make a pipe bomb for him, the charges state.

"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," according to the indictment.

Keebler was impressed with the demonstration from the undercover agent and ordered him to make two more larger pipe bombs, one for the BLM facility in Arizona and the other for law enforcement if they were stopped by authorities, according to the charges.

Late Tuesday, federal prosecutors say Keebler arrived at the BLM building in Arizona and placed an explosive device against one of the doors.

The undercover agent, however, had made an inactive bomb for Keebler.

"Keebler then pushed the detonator button multiple times in order to remotely detonate the inert explosive," the indictment states.

After returning to Utah on Wednesday, Keebler was arrested in Nephi.

His initial court appearance was scheduled Thursday afternoon. If convicted, he faces a potential of 20 years in federal prison with a mandatory-minimum of five years.

Twitter: DNewsCrimeTeam