Police shot a man in Harlem when he allegedly attacked a person with a chain and then threatened police with it, law enforcement sources said. 

Officers responded to a 911 call at 1870 Third Ave. Tuesday evening and encountered the suspect, who was wielding a heavy chain, the sources said.

He struck the victim with the chain and refused police orders to drop it, instead going after the officers twice with the chain. 

Police opened fire, striking the man once, according to the sources. The suspect was taken to St. Luke's Hospital in critical condition.