A shooting in Manhattan's Upper West Side region on Thursday has left four people dead, the New York Times reported.

Three people were shot and killed in their apartment and a fourth man, the suspected killer, was found dead in the backyard.

The three men shot and killed in their apartment at Amsterdam Avenue and West 84th Street were identified as a man in his 20's, his father and his grandfather.

The fourth man found dead in the backyard is believed to either have plunged or accidently fallen to his death while trying to escape.

Police arrived at the scene at approximately 2pm EST.

The motive behind the killings is unknown. A semi-automatic pistol was discovered at the scene.