A rock tumbled off a truck and smashed through the windshield of a nearby car, killing a 75-year-old woman riding by her daughter's side, police and the victim's relatives said.

Police were looking for the truck driver early Thursday, while saying the incident appeared to be accidental. The driver, probably unaware of what had happened, kept going after the accident Wednesday morning, Nassau County Police Detective Gary Ferrucci said.

Rita Oill and one of her daughters, Marie Waters, 39, were out getting supplies for the holiday meal when the three-pound stone came flying at them from a truck headed in the opposite direction on Glen Head Road, police and family members said. Waters was driving, with her mother as a passenger.

After the rock hit the car's hood, Waters "flinched, closed her eyes and ... the piece of debris went through the center of the windshield and struck my mother-in-law in the head," said the driver's husband, Bill Waters.

Oill was taken to a local hospital, where she was pronounced dead. Waters was treated for minor injuries and released.

Oill, of Bayville, was a bowling enthusiast and was active in local elections, "right up to the last one last week," said another of her daughters, Pam Settepani of Croton-on-Hudson.