Chief Tommy Thompson of Jacksonville police said the man robbed the Shell station at 2380 Pelham Road around 6:14 a.m. Sunday. The cashier, a 65-year-old woman, was not injured, Thompson said.
The suspect is believed to be driving a silver Land Rover, Thompson said.
Thompson said the suspect entered the service station first to buy a bottled water, left, then returned 45 seconds later wearing a hooded sweatshirt.
"He jumped the counter and held a box cutter to the woman's throat while he robbed the place," Thompson said.
Thompson said the suspect stole less than $100 from the cash register, then left the business.
"He made her lay flat on the floor after he left," he said.
Thompson urged anyone with information about the suspect to call Jacksonville police at 256-435-6448.
Staff writer Patrick McCreless: 256-235-3561. On Twitter @PMcCreless_Star.