The apparent source of the toxic gas was a maroon Toyota that was left running in an attached garage, said Det. Lt. Raymond Coté, commanding officer of the Williston Park-based Third Squad detectives, who handled the case. "It appears to have been on for quite some time," he said of the car.
The man and woman were found upstairs in the two-story colonial on Meadbrook Road after a home health aide who cares for the couple showed up shortly before noon and called the police when no one answered the door, which was locked, Coté said.
When firefighters forced their way inside, their own carbon-monoxide detectors went off, so they opened the windows before finding the couple dead in separate bedrooms, police said.
"It just looked like they were sleeping under the covers, in their pajamas," Coté said.
Coté said that levels of the poison were very high.
A carbon-monoxide detector in the house was not working. Coté characterized the deaths as an accident with no apparent criminality.
Coté said that in the past the couple's car had been accidentally left on.
Late Thursday night, police named the couple as Catherine, 83, and Joseph Hayes, 87.
Neighbors said the Hayeses had lived in the home for the past half century, describing them as friendly - whether baking for a pregnant woman or giving children Halloween candy.
Christine Pando, 18, a high school senior who lives across the street, recalled how the Hayeses always bought her Girl Scout cookies when she was younger and how Joseph Hayes would let neighbors use his snowblower. "He was always helping everyone," Pando said. "And when he got too old, everyone was helping him."
Eileen Donovan, who also lives across the street, said she would see Joseph going to morning Mass almost every day - in the maroon car that police say was left running in the garage.
"They were nice people. They were religious. They were good people," she said.
On their quiet block, north of Stewart Avenue, west of Nassau Boulevard and south of Jericho Turnpike, the neighbors watched in sorrow as the medical examiner removed the bodies shortly before sunset.