A man carrying a high-powered rifle shot and killed four people, including an off-duty police officer working security in Midtown Manhattan, sources told ABC News.

Officials said the gunman fatally shot himself after his attack, which set off a chaotic scene that rippled out into the heart of Manhattan during rush hour.

The man suspected of shooting dead four people midtown Manhattan last month had years earlier threatened to kill himself as he dealt with depression and concussion symptoms, according to a phone call his mother made to police.