A man was caught on surveillance video carrying a bloody knife down the stairs of a Harlem apartment building Sunday morning after a stabbing there.

The chilling surveillance video from 2795 8th Ave. shows the man gazing at a knife in his hand while walking down the stairs at about 5:30 a.m. after the early morning attack.

A recording from the same camera shows an injured guy being carried down the stairs by emergency workers about 45 minutes later.

The 61-year-old victim, whose name was not immediately released, was rushed to Harlem Hospital in critical condition, police said.

The 52-year-old alleged slasher turned himself into police and was facing charges, cops said. Police did not yet reveal what the men were fighting about.