Shortly after 6 Tuesday morning, Morehead police said they were notified of an alarm going off at the Sonic on US Highway 60.
When they got there, the store's manager, 32-year-old Jason Allen, said he had been robbed and assaulted.
He told officers he had been stabbed in his face, hands and body, and had also been struck in the head.
The attacker is described as a 40-year-old white male, standing 6' 2" with short brown hair and blonde tips, with a cross tattoo on his right hand.
The suspect was last seen wearing a black sweatshirt, blue jeans and a black toboggan.