An NYPD sergeant found his elderly parents and their two friends dead in an apparent case of carbon monoxide poisoning in Floral Park Friday afternoon, sources said. View Full Caption DNAinfo/Katie Honan

QUEENS — An NYPD sergeant found his elderly parents and their two friends dead in an apparent case of carbon monoxide poisoning in Floral Park Friday afternoon, sources said.

Sgt. Robert Hugel couldn't reach his parents on Friday afternoon after his shift, so he went to their house at 260-08 86th Ave. in Floral Park, sources said.

When he got there, Hugel found a Chevrolet idling in the garage and his 83-year-old father Jerry Hugel collapsed next to the vehicle, which was believed to be the source of the poisonous gas, police at the scene and sources said.

Emergency responders found the three others scattered across the home. Hugel's 80-year-old mother Marie was found in a kitchen basemen and 76-year-old Walter Vonthadden, who was visiting the family, was dead in the living room.

Their upstairs tenant, 70-year-old Gloria Greco, was collapsed in a second-floor hallway.

Medics pronounced them dead shortly after they arrived around 3:15 p.m.

The deaths were believed to be an accident, police sources said.

A friend of the family's said she rushed over from her Bellerose home when she heard the tragic news.

Helga Harter knew Jerry and Marie Hugel for four decades.

Harter said Jerry and Marie were members of Schlierachtaler Stamm, a Bavarian Dance club. Jerry was president of the club up until 2013, the club's homepage states.

"They were a great couple," she said. "Very involved in (German) dancing. They went to Germany every year twice."