A man was killed Wednesday night when an off-duty FDNY ambulance slammed into him as he tried to cross a highway, police said.

The unidentified 89-year-old was struck just after 8 p.m. on the Cross Island Parkway near 109th Avenue in Queens.

He was transported to North Shore Manhasset Hospital, where he succumbed to his injuries.

Three emergency service personnel were riding in the ambulance at the time of the fatal accident. They tried to provide aid for the victim at the scene until assistance arrived, cops said.

All three were taken to Long Island Jewish Hospital as a precaution and are in stable condition, officials said.