Police are investigating after finding a 53-year-old man dead in his Upper East Side apartment building with an apparent stab wound.

Officers responded to the building on East 85th Street shortly before 7 p.m. and found Hector Rossy unconscious at the scene, according to the NYPD. EMS crews pronounced him dead on arrival.

Medical examiners will determine exactly how he died.

No arrests have been made.