Davie, FL- An elderly Davie couple accidentally left their car running in their garage overnight Saturday, filling their home with deadly carbon monoxide.

Their deaths have been ruled accidental.

David and Dorothy Roth, 88 and 83, were found dead by their son inside their home after they didn’t show up for a planned dinner, according to Lt. Bill Coyne, a Davie police spokesman.

The couple’s dog also died in the accident.

Here’s how Coyne said it happened:

David Roth was disabled and used a wheelchair. The couple’s vehicle had a motorized chairlift that only ran when the car’s engine was running.

The working theory is that Dorothy Roth forgot to shut off the car after helping David into their home, 3171 Overlook Rd., Saturday night — a mistake she had made before.

For hours, the airtight garage filled with the poisonous gas.

The next morning, Dorothy realized the vehicle was still running, went to turn it off but didn’t make it back into the house before collapsing. She did, however, leave the door open. David tried to help her, but he, too, was overcome.

The gas then spread through the rest of the house, killing the dog, which was sleeping on their bed.

Their son made the macabre discovery about 8 p.m. Sunday.

”It’s an unfortunate accident,” Coyne said. “This just shows a smoke detector isn’t enough. You should have a carbon monoxide detector, as well.”