Strong arm robbery? Are you aware that the store did not call in a robbery? They didn't report it. A bystander who had no idea what happened called it in as being suspicious. At no point did the store call the police to report a robbery.
And the whole pot affects impairment only seems to come from people who have never smoked pot. It's a downer. It chills you out. It doesn't make you violent. The complete opposite actually.
You're just another person giving an opinion of what you think happened based on your narrow view of the black community without knowing any of the people involved.