A man was killed Saturday night after his car swerved off the highway in Webster and struck a tree in the median, State Police said.

Police responded to a report of a single-car crash around 9:15 p.m. just south of Exit 3 on the northbound side of Interstate 395. The man, who was alone in the car, was removed from the 2006 Chevrolet HHR and pronounced dead at the scene, police said.

The cause of the single-car crash is under investigation.Police are withholding the identity of the victim until his family is notified.

Alexander Schroeder can be reached at alexander.schroeder @globe.com.He tweets @alexjschroeder.