Police arrested a Bountiful man on Sunday after he allegedly plotted to kill several people with firearms and explosives and tried to enlist a co-conspirator, according to charging documents.

Robert Jack Turville, 62, allegedly tried to engage a co-worker at a Midvale sporting goods store to help him kill five people, including with explosives planted in vehicle headrests, a Unified Police Department probable cause statement said.

Unified Police detective Ken Hansen said Monday the co-worker secretly recorded the alleged threats and criminal solicitation. That employee contacted police on Friday, Hansen said.

“With the nature of the threats being so specific, it required a lot of urgency,” Hansen said of the investigation. “We’ve had four detectives on this since Friday, just to make sure, because there was a big concern for the potential victims.”

Read more: Standard-Examiner (Ogden, UT)