According to the police report, it appears that “Dorian Johnson” was an accomplice to the strong arm robbery of the store clerk and therefore could be charged with felony murder for the death of Mr. Brown.
I'm not so sure. Not an attorney, but I suspect these would be considered separate but related incidents. Had Brown been killed at the store during the robbery, you would certainly be right, though MO law might be different from other states.
Does anybody know how much time elapsed between the robbery and the shooting? How far apart are the locations?