Joseph Szemcsak, 76, of East Windsor, N.J., was taken to Brookhaven Memorial Hospital Medical Center, where he died after the 4:54 p.m. accident.
Leach had been driving south on Patchogue Yaphank Road, County Road 101. He had minor injuries and was taken to a hospital for treatment. Three passengers who were also in the car with Leach were hospitalized, with injuries that were not considered to be life-threatening.
The investigation is continuing. Detectives ask anyone who may have witnessed this crash to call Suffolk police Fifth Squad detectives at 631-854-8552.