SAN FRANCISCO (KPIX 5) – A San Francisco firefighter is under arrest, accused of stockpiling an arsenal of high-powered weapons and making threats to kill.

Rock Plichcik was arrested after authorities said they discovered more than two dozen guns at his home, violating a protective order against him.

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Authorities said half of the guns found were assault rifles.

Investigators with the Bureau of Alcohol, Tobacco and Firearms said they received several tips that Plichcik had “assault weapons, including a machine gun, multiple AR-15s, multiple AK-47s, live grenades, ammo and … Hundreds of firearms.”

The tipsters described Plichcik as “mentally ill” and “violent” after he posted a YouTube video where he was allegedly “threatening to kill everyone and open fire…on a Smart train.”

Rock Plichcik. (San Francisco Police Department)

Rock Plichcik. (San Francisco Police Department)

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A source told KPIX 5 that investigators arrested Pilchcik where he worked, Fire Station 22 on 16th Avenue, on Monday afternoon.

Court documents said he denied owning guns to San Francisco police, but a search of his home told a much different story.

As for the protective order filed against him, court documents said his sister requested the order after a battle over $1.6 million. Pilchcik’s sister said the firefighter “threatened to kill her numerous times” and she was “fearful if he was released.”

A spokesperson with the San Francisco Fire Department declined to comment.

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Pilchcik pleaded not guilty in court on Thursday. He is expected to return to court later this month.