My heartfelt sympathy goes out to the deceased's widow and family.
This incident was a criminal act.
To start trying to apportion blame to airport security, the police, airport management is missing the point.
This incident probably lasted less than a minute. Unless you have police and/or security officers patrolling the front of the terminal at all times when it is open, it is completely unrealistic to say they could have prevented it. And if you did they would have had to have been very close to the car in question. Remember these thieves thought it was an easy touch and I am sure did not expect resistance from the owner. Had it gone to the thieves' plan it would have been over in less than ten seconds with the stolen car and thief away.
Let us accept that we have violent criminals in this country and let us try to get society as a whole to accept that and not pussyfoot around with them when they are caught. This is preferable to playing armchair detective. It is a bit like non pilots saying what they would do or would have done in the event of an airborne emergency.