I don't think handing out tickets and breaking up domestic disputes is worthy of a death sentence by vigilante. You have no standard by which to judge this man's action's other than a uniform. An eye for an eye would make the whole world blind. I think Shaw's ad hom sticks in this case.
They don't just hand out tickets and break up domestic disputes. They are in the business of intimidating the citizens into complying with blatantly unjust laws.
At the Battle of Bunker Hill, there weren't "good" and "bad" Redcoats, only enemy Redcoats. Killing a thousand of them wasn't excessive, because they still took Breed's Hill. Likewise, taking out one enemy officer in San Antonio was not excessive, because cops still enforce unjust laws.
That's why I advocate not catching the license plate number if you see something like that happen.