PALMER PARK, Md. — A Maryland man who called himself “a joker” and had an arsenal of semiautomatic rifles threatened to shoot up the business from which he was being fired and was wearing a T-shirt that read “Guns don’t kill people. I do,” when first confronted by officers, police said Friday.

The man, identified as Neil Prescott, told a supervisor at software and mailroom supplier Pitney Bowes that “I’m a joker and I’m gonna load my guns and blow everybody up,” and that he wanted to see the supervisor’s “brain splatter on the floor,” according to a search warrant Friday.

The threats were made multiple times in separate phone calls this week, and investigators who searched the 28-year-old’s apartment Friday morning found several thousand rounds of ammunition and about two dozen firearms.

He was receiving a mental health evaluation at a hospital, and charges were pending.

Last week’s mass shooting at a Colorado theater during the latest Batman movie — coupled with the joker reference — put police especially on edge and gave the comments extra urgency, officials said.