The gunman behind the 1984 “Palm Sunday Massacre” that left 10 people dead in one of New York City’s largest mass shootings in decades was quietly released from prison in January.

Christopher Thomas, 68, was released from Shawangunk Correctional Facility January 5 and is believed to be residing in Queens, NY, the New York Post reported. He was released after serving about two-thirds of his 50-year maximum sentence, good behavior and fulfilling other criteria, according to a New York State Department of Corrections spokesperson. “The parole board did not let him out,” the spokesperson said. “He had five appearances before the parole board and was denied every time. He doesn’t need board approval because he served two thirds.”

Thomas was convicted of manslaughter and sentenced in 1985 to 25 to 50 years. He avoided a murder conviction because it was determined his heavy cocaine usage “contributed to his actions,” the New York Post reported.

A sole motive for the slaying was never determined.

On Palm Sunday in 1984, Thomas shot and killed 10 people in an apartment in Brooklyn. Thomas was embroiled in a dispute with the apartment owner, convicted drug dealer Enrique Bermudez. The victims of the slaying were Bermudez’s pregnant wife, another adult woman, and eight children.

One person survived the shooting, a toddler named Christina Rivera, who was adopted by a police officer at the scene of the slayings, The New York Times reported.

Ray Kelly, the former commissioner of the New York Police Department said Thomas’ “heinous crime warranted the maximum penalty.”

Retired NYPD Lt. Herbert Hohmann told the New York Post Thomas does not deserve to be free.

“He doesn’t deserve to be on the street. He killed poor, innocent children,’’ Hohmann said.