Police say 87-year-old Gerard Paul, of Holbrook, was pronounced dead at the scene Thursday.
Police say his car went off the end of Union Avenue, struck a dirt mound, and flipped over sometime on Tuesday. The car, which was not visible from the roadway, was found by electrical contractors working in the area.
Suffolk County Police had issued a Silver Alert for Paul on Wednesday. The alerts are issued for individuals with special needs who have been reported missing.