Been trying my hardest to stay out of this convo because my family and friends on Facebook have been going insane and I'm tired of the whole thing, but:
Apparently Mike and his friend attempted to buy a box of cigars (the box you see his friend put on the counter) and did not have enough money for the box, so Mike decides since he's given the clerk the money for the box to grab a handful of the cheaper brand singles that the money he gave the clerk would cover and in doing so the box spills on the floor. It was an unnecessary dick move on Mike's part (he didn't need to get angry at not having enough cash for his purchase and then aggressively take the singles from the box, he could/should have just said "Fine, I'll just take the singles"😉. Anyway, he grabs a few of the singles from the floor and walks away. The Clerk comes around to ensure he didn't take more than he had paid for, Mike shoves Clerk for 'coming at him', and leaves. While this exchange occurs someone else present in the store assumes it's a robbery and calls 911.
Mike and his friend, however, were stopped for walking in the middle of the street, not a robbery pursuit, so this incident, while showing Mike made a dick move, had no connection to the shooting. It does, however, show that he was prone to unnecessary aggression. He didn't need to spill the cigars and disrespect the Clerk because he didn't have enough money for what he wanted.