An arsenal of illegal guns -- including assault weapons and a silencer -- have allegedly been found in the sparsely furnished New York apartment of a pizza delivery man who police say was harboring a grudge.

Suffolk County Police Chief Stuart Cameron said cops went to the Lindenhurst, Long Island, home of Robert Csak, 32, on Saturday night to do a welfare check. Earlier that day another police department had advised the Long Island officers that Csak left "threatening" messages on the voicemail system of his former high school.

When his landlord opened the door, police were met with a pile of weapons in an apartment otherwise furnished with only a mattress and a plastic chair.

[NATL-NY] See It: Police Seize Enormous Cache of Weapons From Long Island Man's Home

Among the arsenal: nine illegal guns, assault weapons, hundreds of high capacity magazines, a silencer and a bump stock -- an attachment that makes a semi-automatic weapon shoot nearly as fast as fully-automatic machine guns.

“This is by far the most alarming threat we’ve seen," Cameron said. ”There’s many commonalities between his behavior and the behavior of mass shooters."

Concerns had been raised about Csak after he left a message for a staff member at Summit School in Nyack. Cameron said Csak felt slighted by the staff member he left a message for, and was carrying a grudge.

Suffolk County Police

Clarkstown Police said a 45-year-old school employee reported getting six messages on the school's voicemail from Csak, and he was concerned for the safety of the students.

Csak attended the school for teens with learning and emotional difficulties in 2002.

“We really never know what we averted, but if you look at all those weapons you know there was a lot of potential here," Chief of Detectives Gerard Gigante said.



Csak was arrested Saturday night and will face numerous weapons charges. Attorney information was not available for Csak. He's due to be arraigned Monday.

WHAT POLICE ALLEGEDLY FOUND

19 various firearms, including 1 tactical shotgun, 1 Tommy gun and more than 200 high-capacity magazines

1 bump stock (used to create an automatic weapon out of a semi-automatic weapon)



1 cross bow

Night vision goggles

1 silencer

Bulletproof vests

Gas masks

Knives

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