I call malarkey. Was he trained to shoot to kill or defuse a situation?
Depends on what time period you are talking about. These days cops "don't have time" to defuse the situation, and their departments are supporting this approach by buying military equipment and organizing SWAT teams, and by clearing officers of any wrongdoing if they happen to kill someone without a good reason.
If he was presented with a situation that he believed was an instant threat to great bodily harm or was life threatening he has been trained to respond instantly with deadly force. Not malarkey at all. All of the witnesses said the victim through a container of popcorn at him just before he got shot. The victim was in the row right below the shooter so there was maybe three feet between them.
Cops are trained to defend themselves, period. They make this decision in less than half of a second. He made the wrong decision but he did follow what he had been trained to do.