A 27-year-old man wearing body armor and carrying a high-powered M4 rifle shot and killed four people, including an off-duty police officer working security in a Midtown Manhattan office building, officials said during a press conference Monday evening.

The incident occurred just before 6:30 p.m. in a building located at 345 Park Ave. and 52nd Street, which contains the headquarters for the investment company Blackstone and the National Football League, sources told ABC News. It is unclear if those companies, or any company in the building, were tied to the shooting. After apparently barricading himself on the 33rd floor, the suspect, who was identified as Las Vegas resident Shane Devon Tamura, was found dead from what is believed to be a self-inflicted gunshot wound, according to New York Police Department Commissioner Jessica Tisch.

During a press conference on Monday evening, Tisch said preliminary information suggests the suspect traveled cross-country by car from Las Vegas before arriving in New York City. Tamura had a license to carry a concealed weapon in the state of Nevada. The man emerged from a double-parked BMW in front of the office building and entered the lobby alone and immediately opened fire on an NYPD officer and sprayed the lobby with bullets, Tisch said.