LINDENHURST, N.Y. (CBSNewYork) — A Lindenhurst man is facing multiple weapons charges after cops discovered nearly two dozen firearms, along with high-capacity magazines and an alarming cache of tactical gear, inside his home on Sunday during a search prompted by a “threatening message left at a school” in Rockland County.

Police in Suffolk County say they were notified by officials from the Clarkstown Police Department to check on Robert Csak, 32, after he left a series of threatening voicemails, directed at an employee, on the answering machine of the Summit School in Upper Nyack on Saturday.

robert csak Long Island Man Arrested With Arsenal Following Threatening Calls To Former School, Cops Say

Robert Csak, 32 (credit: Suffolk County Police)

Csak attended the school for youth with emotional and behavioral issues in 2002 and was identified through caller ID and school records, according to police.

“From every indication we have now he felt slighted by this individual from an encounter back in 2002 and was carrying a grudge,” Suffolk Police Chief Stuart Cameron said.

Csak wasn’t home when officers arrived, so police say his landlord let them into his house on 38th Street where they observed a tactical shotgun, crossbow, night vision goggles, high-capacity magazines, and an assault-style weapon.

After securing the apartment and obtaining a search warrant, officers recovered an additional 19 firearms, a silencer, more than 200 high-capacity magazines, a Tommy gun, an additional set of night vision goggles, bulletproof vests, gas masks, knives, asps, and a bump stock.

Authorities say the pizza delivery driver was arrested while on the job late Saturday at a red light and is facing multiple charges of criminal possession of a weapon.

Csak’s landlord of roughly two years says he had no idea his tenant was hiding the arsenal in his home.

“He kept to himself, you know, didn’t say much,” he said. “He came and went, I’m his landlord you know? Paid his rent on time and was always nice to me and texted me. Never really gave me any trouble.”

Csak is expected to face a judge Monday.