"What was going through my mind at that point was that the security tape is either going to show me run away and hide in the office or whack this guy in the head, so I just grabbed the cup and clocked the guy pretty hard."
It's good that the robber was killed.
But actually, many in law enforcement and in the business world teach clerks and cashiers not to resist when thieves come along. Resisting can get you killed.
But YouTube offers instant fame, and everyone knows it...
