Behrouz Benyaminpour, 54, was driving a 2007 Toyota Camry east on Route 25, just east of Colonial Drive, when he crossed the double-yellow line into oncoming traffic at 12:49 p.m., according to a police report.
Benyaminpour's vehicle caused a 1998 Jeep Cherokee driven by Carlene Devito, 65, of Hampton Bays, to swerve, sideswiping a 2005 Honda Accord. The driver of the Honda, Courtney Riso, 28, of Jamesport, then collided head-on with a Hyundai Elantra, driven by Joseph E. Fulcoly IV, 18, of Calverton.
A passenger in Benyaminpour's car was airlifted to Stony Brook University Medical Center with head trauma and later pronounced dead, police said.
Updated information on the injured was not immediately available.
Police have not released the name of the person who died. They said an investigation is continuing and asked witnesses to call 631-727-4500.