HOPE, Maine — Investigators with the Knox County sheriff’s office are continuing to collect and review surveillance videos to try to find a truck that may have been the source of a large rock that struck and killed a motorist on Tuesday.

Chief Deputy Tim Carroll said Thursday that investigators were reviewing videos from cameras located at businesses along Route 17, but that a truck had not yet been identified.

James Nash, 73, of Camden died instantly when a rock that was 6 to 8 inches in diameter came crashing through the windshield and struck him, Carroll said.

His wife, Marilynn, who was a passenger, was able to keep her composure enough to gain control of the car from the passenger seat and coast it to a safe stop. She suffered minor injuries and was treated for shock but was released from the hospital the evening of the incident, the chief deputy said.

She believes she briefly saw a truck heading in the opposite direction but that her attention was drawn to a large object coming at them so she was not able to provide a better description, Carroll said.

The car was about 300 yards west of the intersection with Wotton’s Mill Road shortly before 3 p.m. Tuesday when the accident happened. The Nashes were headed east in their 2013 Honda Civic and the truck was headed west, according to police.

Sheriff Donna Dennison said Wednesday that investigators weren’t sure yet whether the rock fell off the back of a dump truck or could have fallen off a flatbed truck or even been kicked up by the tires of a truck.

While it is not clear yet what happened in this case, there are laws concerning the securing of loads on trucks traveling Maine roads, Lt. Brian Scott of the Maine State Police traffic safety division said Wednesday.

Maine law states “a load of gravel, sand, crushed stone, rubbish, building debris or trash must be covered or otherwise secured or confined to prevent any portion of the load from falling from or spilling out of the vehicle.” The fine for violating the unsecured load law is $190.