Ammon News - A gunman armed with an assault-style rifle killed four people inside a Manhattan skyscraper that houses the headquarters of the NFL and offices of several major financial firms and then shot himself dead, New York City officials said on Monday.

One of the four victims slain in the gun violence was a 36-year-old New York Police Department officer who immigrated to the U.S. from Bangladesh.

Authorities offered few details about the three other victims killed by the suspect - two men and a woman. A third male was gravely wounded by the gunfire and was "fighting for his life" in a nearby hospital, the mayor said.

New York Police Commissioner Jessica Tisch said the gunman, identified as Shane Tamura, 27-year-old Las Vegas resident with a history of mental illness, had driven cross-country to New York in recent days.

The gunman was believed to have acted alone, and investigators had yet to determine a possible motive for the shooting, Tisch told reporters at a late-night news briefing. Reuters