A customer went on the attack when a Long Island gas station clerk, suspicious that the customer was trying to pay with a fraudulent card, asked for identification, police say.
Police released surveillance video Friday in the brutal Nassau assault from January. It shows a man in a red hat going behind the counter and launching the assault.
"This guy quickly engaged in violence. It looks like he was set off and went at it," said Nassau Police Chief Kevin Smith.
The clerk suffered a skull fracture and torn knee ligaments in the assault. He has since left the job, workers at the station told NBC4 New York Friday.
Police are releasing the video five months after the attack because leads in he case have been drying up.
In addition to the attacker, they're also seeking the female companion who watched the entire assault.
"We have to get this guy off the street," said Tiffany Boyd, a customer at the station. "He shouldn't have the potential to do this to anyone else."