The suspect walked into the store in the 10700 block of 5th Avenue NE just after 7 p.m. with his shirt pulled over his face and flashed a knife at the store's owner, said Patrick Michaud of the Seattle police.
When the suspect demanded money, the store owner gave him some coins from the register.
The suspect demanded the paper money from the register as well, but was interrupted when other customers entered the store.
The suspect became flustered and fled on foot only to be chased down and subdued by two witnesses, who held him until officers arrived, Michaud said.
Officers took the suspect into custody and booked him into King County Jail for investigation of robbery.