PALMER PARK, Md. – A Maryland man who called himself "a joker" and had an arsenal of semi-automatic 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 in a search warrant as Neil E. 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 all over the sidewalk," according to a police officials and a search warrant.

The threats were made two 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 semi-automatic rifles and pistols. He was receiving a psychiatric evaluation at a hospital and charges were pending Friday.