The man who killed UWS’ grandmother was a former building superintendent, prosecutors said.

On Sunday, prosecutors said the man accused of killing a grandmother in her Upper West Side apartment was once the building’s interim superintendent.

LaShawn McKee, 47, was arrested Saturday for the murder of Maria Hernandez, 74, at her home on 83rd Street, just off Columbus Avenue, police said.

Hours after they attended a Broadway matinee and had an early Wednesday dinner, Hernandez’s sister discovered a dead woman in the apartment.

Police said she was strangled, her hands and feet were tied, and her mouth was gagged.

At the arraignment in Manhattan criminal court on Sunday, prosecutors laid out the gruesome details of the brutal murder.

“This is a particularly brutal murder where the victim was found beaten, bruised, beaten, with her hands and feet tied behind her back, lying face down under a pile of clothes in her bedroom,” they said. “Victim died of fatal asphyxia with concomitant neck compression.”

The prosecution said there was also evidence of cuts to Hernandez’s private parts.

Before he allegedly killed Hernandez, McKee broke into the superintendent’s office in the building’s basement to retrieve the security video recorder.

“It was clearly a premeditated crime,” the prosecutor’s office said.

Meanwhile, McKee’s lawyer said her client was “shocked” to learn that he was suspected of killing a Dominican immigrant.

“Despite any connection they say they have regarding Mr McKee’s work in the building, it appears that in this case there is no surveillance by the victims that would actually show Mr McKee on the third floor where, according to they say it happened.” said lawyer Jessica Horani.

After serving time behind bars for assault in 1999 and serving parole, McKee took a job at the building, though it’s not clear exactly what year he worked there, a New York County Defense Services attorney said.

“He stands before you categorically denying the allegations against him,” Horani added. “I don’t believe people have hard evidence in this case.”

McKee of Crown Heights was held without bail after the hearing.

He has been charged with murder, attempted murder and burglary.