Police released disturbing video Thursday of a man creeping up on an on-duty traffic agent in Staten Island — and knocking him out with a punch to the neck.

The footage shows the suspect chatting on the phone, moments before he sneaks up on the unsuspecting 50-year-old near Heberton St. and Post Ave. in Port Richmond around 3 p.m. Wednesday.

The attacker then punches the victim in the neck.

The traffic agent fell to the ground and lost consciousness, officials said.

He was rushed to Staten Island University Hospital North where he was treated for a head injury and bruising to the neck.

The suspect is believed to be in his 20s and was last seen wearing a black t-shirt and gray pants, police said.