Investigators found a military backpack, glass tubes and kitty litter on the passenger floorboard of a car belonging to a man who gunned down the general manager of Eldora Mountain Resort last week, according to a search warrant affidavit released Wednesday.
Dressed in black with a magazine holster strapped to his left thigh and a gun holster on his right thigh, Derik Bonestroo seemed to have planned the Dec. 30 attack that killed 49-year-old Brian Mahon, Detective Chris Fiegel wrote in the affidavit.
Bonestroo, 24, of Nederland, died during an ensuing shootout with a Boulder County sheriff’s deputy, and was “clutching a ‘glock’ semi-automatic handgun in his right hand,” Fiegel wrote in the affidavit, which outlined belongings found in Bonestroo’s car, apartment and parents’ home.
The items in his car sparked initial suspicion that Bonestroo had planned to make an explosive device or mobile meth lab, although Boulder County Sheriff Joe Pelle said no explosives have been found.
“But they did find a lot of ammunition,” Pelle said.
Bonestroo moved to a single-story home in Nederland in November, when he started working at Eldora, according to authorities.
Among the list of items confiscated from Bonestroo’s apartment were medication and a dead cat that had been stabbed several times, Pelle said.
Other items taken from his apartment include: an empty glock magazine, a digital camera, an Apple laptop, a spiral notebook, a bank card, a small-game hunting license, a cell phone and a friendship bracelet.
From Bonestroo’s bedroom at his family’s home near Longmont, where he spent Christmas Eve, detectives found several rifle cases. Pelle said Bonestroo previously worked at a gun shop and studied gunsmithing at Trinidad State Junior College, a community college in southern Colorado.
“It seemed to be an innocent interest,” Pelle said.
Bonestroo’s father told police his son had two handguns in his possession when he moved out, Fiegel wrote in the affidavit. But, Pelle said, the family didn’t know anything about Bonestroo’s intentions with the weapons.
The morning of the shooting, Bonestroo â a lift operator at Eldora â told his co-workers, “If you’re not Christian, you’re going to die.” When he asked Mahon to state his religion, Mahon said “Catholic,” and Bonestroo shot him in the chest and head.
Witness April Wilson told investigators everyone ran when Bonestroo fired. She escaped into “the woods and as she was running recalled hearing an additional four to five shots being fired,” Fiegel wrote.
Interviews with friends and family members have indicated Bonestroo recently had been suffering “significant emotional distress,” but Pelle said privacy laws prohibit him from discussing details of Bonestroo’s mental state.
He did say people experiencing a “mental health crisis” often fixate on something.
“Some times it’s religion and some times it’s other things,” Pelle said. “I don’t know that this was about religion as much as it was a mental-health crisis.”
Pelle said an investigation of the homicide and officer-involved shooting will wrap up next week, and his office will release the results of those investigations at that time. Boulder County Coroner Tom Faure said it will be several weeks before his office will have Bonestroo’s toxicology report.