An ice-cream deliveryman may have inadvertently contributed to his mom’s death — caused by cases of dry ice he kept stashed in his car, officials said.

The unidentified man said his wife agreed to drive his mom home last Thursday night, but early the next day, he found them unresponsive in his car surrounded by coolers of dry ice, the Tacoma News Tribune reported.

“He had four coolers full of dry ice because he delivered Dippin’ Dots to various location,” said Pierce County Sheriff’s spokesman Ed Troyer, referring to the ice cream treat. “Somehow or another, the fumes escaped from the coolers.”

The 77-year-old woman died at St. Joseph Medical Center in Tacoma and her 51-year-old daughter-in-law is still in critical condition.

Investigators said the new car’s sealing may have created a confined, non-ventilated space that turned the ice deadly.

Dry ice, a solid form of carbon dioxide, transforms to gas when exposed to open air, and can be lethal in poorly ventilated areas.

“Possibly because it was so hot outside and because he had a newer car. It probably had better sealing and less ventilation. It was a combination of things that went terribly wrong,” Troyer told KOMO news.

“This all happened due to a lot of circumstances lining up. dry ice by itself isn’t going to kill anybody,” he said.