When the Snohomish County, Washington dispensary Dexter Warren worked at was robbed last year, four men simply walked in. When one of those men hit him in the face with a pistol and demanded he open the safe, the cash-based business had thousands of dollars on hand, he said. By the time law enforcement arrived 20 minutes later, the men had already left with money and merchandise, said then-assistant manager Warren. On Saturday, a man working at a Tacoma cannabis retailer was shot, the third fatality related to a cannabis shop robbery within four days. On Wednesday and Thursday, two men each ac…