NEW YORK (CBSNewYork) – An active crime scene on the Upper East Side is raising a lot of questions about the unexplained death of a resident.

The medical examiner along with the NYPD crime scene unit were on-site in unit 1D of an apartment building on East 83rd Street after a man was found with a gash to his head, lying in a pool of blood.

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Police were not letting anyone in the building on Wednesday night, reports CBS2’s Jessica Layton.

Sources say a friend went to check on the 64-year-old after he hadn’t heard from him in a while. Police say that’s when he found the resident dead on his living room floor.

Initially, police thought he had fallen and that’s what caused the head injury, but there was no furniture or objects near him that would have caused the injury.

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The building near East 83rd and Lexington is next to the Metropolitan Republican Club. The scene has shaken up neighbors who call the victim a great guy and a man of faith.

“Kept to himself, would come home from work, drop his bag off, go out to church at 5:30,” said neighbor Charles Franck. “(He would) come home ten after 6, always friendly, always kind, always waved, a beautiful man.”

“Obviously it’s concerning if there’s an apparent suspicious death,” said neighbor Andrew Fine. “Crime is slowly creeping up, it’s important to be vigilant.”

Police won’t release the name of the victim until his family has been notified.

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Authorities are not calling this incident a homicide yet or saying if the neighborhood should be concerned for safety.