Simpson is the third suspect to face charges in the case. 24-year-old Stephan Cannon is accused of shooting Dorn outside the shop. He's charged with first-degree murder. 27-year-old Jimmie Robinson is charged with burglary, armed criminal action and stealing.
The search continues for several other persons of interest in the incident, who were seen on surveillance video released by police.
CrimeStoppers of St. Louis is still offering a $45,000 reward for information that leads to an arrest and charges related to the murder.
On Wednesday, a private funeral was held for Dorn. Here's a live stream of the procession: