PORTLAND, Ore. (KOIN) — The man who sold the gun used to shoot and kill a Cowlitz County deputy in 2019 was arrested Wednesday in Cathlamet, Washington, on charges of manufacturing untraceable firearms, police said.

According to the Longview Police Department, Trevor Batchelor was taken into custody after a SWAT team delivered a warrant to his door and detectives found hundreds of items related to assembling guns.

Police said authorities uncovered evidence as far back as the fall of 2018 that Batchelor was selling guns without a license — including an undercover deal where he was caught on camera — but he was let off with a warning from federal agents: stop or face criminal charges.

About seven months later, one of the guns Batchelor had sold was used to kill a Southwest Washington deputy, officials said.

Connection to DeRosier’s shooting death, Butts family

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Brian Butts

LPD said Batchelor sold the gun that 33-year-old Brian Butts used to shoot and kill Deputy Justin DeRosier on April 13, 2019.

That night, DeRosier responded to what seemed to be a routine report of a disabled mobile home blocking Fallert Road in Kalama.

Minutes after his arrival, DeRosier was fatally wounded by Butts and died the next day. Butts was a convicted felon and prohibited from owning a gun, police said.

He was killed the next night in a standoff with Kelso police officers.

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Daniel Butts in court Tuesday Feb. 6, 2018. (KOIN)

DeRosier, 29, was the first Cowlitz County deputy to die in the line of duty in the agency’s 165 years — and it was the second shooting death of a law enforcement officer for the Butts family.

In January 2011, Brian Butts’ half-brother, Daniel Butts, shot and killed an Oregon police chief. Rainier Police Chief Ralph Painter was shot while responding to a car audio store. Police said Daniel Butts was trying to steal a car at the time.

In April 2019 after DeRosier’s death, federal agents and LPD detectives interviewed Batchelor about the Smith and Wesson 9mm handgun used to shoot the deputy. Police said Batchelor told them he pawned the gun for cash at a local shop, but after checking the pawn shop’s records, authorities found the pistol never went through the business.

The investigation into Batchelor

Police said Batchelor’s arrest Wednesday is the culmination of a sweeping three-year investigation that enlisted the help of agents from the Bureau of Alcohol, Tobacco, Firearms and Explosives.

The investigation began in March 2018 when a community member reported Batchelor to the ATF over concerns he was selling guns without a license, authorities said.

And in August 2020, authorities again brought in Batchelor for questioning. When detectives asked him about other guns he bought, Batchelor told them he couldn’t remember to whom he sold the weapons, LPD said.

Authorities said they then started working with an unnamed source who knew about Batchelor’s gun trades — and helped them conduct purposefully illegal sales with him, including one gun with no serial numbers.

According to LPD, Batchelor knew the buyer wasn’t legally allowed to own one, and detectives used the evidence to get a search warrant.

KOIN 6 News will update this story with more details.