A 27-year-old Amityville man was arrested after police say he struck a defenseless 67-year-old man with a baseball bat to the head.

According to Nassau police, Josue Philippe Jeannoute assaulted the victim as he was walking to his vehicle after leaving the post office in South Farmingdale.

The unnamed victim sustained multiple injuries and was transported to a local hospital or treatment.

A good Samaritan who witnessed the attack called police and followed Jeannoute from the scene.

NCPD credited the witness and cooperation with Suffolk police for the successful apprehension of the suspect.

Jeannoute faces assault and criminal possession of a weapon charges.