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.

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.