Bellingham Police Sergeant Mike Scanlon says two white men in their late teens or early 20s walked into the Shell station on Holly Street and ran out with a case of beer without paying for it.
The cashier chased the men when one of them pulled out a foot-long knife.
Sgt. Scanlon say police would prefer that people not put themselves in harms way over stolen property.
The cashier wasn't hurt.
The man with the knife was described as 6 foot 2 inches, with blonde hair and a scar on his lower lip.
The other man was about 5 foot 10 inches with red hair.
Officers are reviewing security camera footage, but anyone with information is asked to contact Bellingham Police.