The shooting took place in Lawrence Township around 12:25 a.m. Tuesday.
Authorities say no other injuries were reported.
The man's name has not been released.
Investigators say someone opened fire, possibly inside the restaurant.
Police are searching for the driver of a black Chevy Suburban who took off after the shooting.
Detectives and the Mercer County Prosecutor's Office remain at the scene as the investigation continues.
(The Associated Press contributed to this report.)
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