Four people, including the elderly relatives of an NYPD sergeant, died on Friday of what is believed to be accidental carbon monoxide poisoning in Queens.

Police say the bodies of four people—Jerry Hugel, 83, his wife, Marie, 80, their tenant Gloria Greco, 70, and Walter Von Thadden, 76—were found around 3 p.m. on Friday at a home on 260th Street near 86th Avenue in Queens. The News reports that Jerry Hugel was found in the garage next to an idling Buick, while Marie Hugel was found in a basement kitchen near the garage. They were reportedly found by their son, Sgt. Robert Hugel, a member of the NYPD’s Technical Assistance Response Unit.

It is believed that all four died of carbon monoxide poisoning because of the car fumes. "It looks like it was an accident, someone just forgot to turn the car off," a source told the News. "The windows were air-tight, so there was nowhere for the gas to go."

The Times writes:

Raj Patel, another neighbor, said he saw Robert Hugel weeping outside the home just after 3 p.m. Mr. Patel said he overheard the police saying the car in the garage was a Hyundai owned by the upstairs tenant who had turned it on with an automatic starter on her key chain and then left it running through the night.

"It is very surreal,” neighbor Barbara Stoja told the Post. "We knew them for over 35 years. They were very fun people; they were dancers." They added that the German-immigrant couple, who had five children, led a Bavarian dance troupe called the Schlierachtaler Stamm Club.

Queens City Councilman Mark Weprin said in a statement, "It is my hope that this tragedy sheds light on the importance of having, and maintaining, a carbon monoxide detector in all homes and apartments."