In Texas, we could have legally capped that cop. Texas State Law allows use of dealdy force on LEOs when they use greater than necessary deadly force.
Note to Mindbender twentywhatever: I have no wish to harm LEOs. Let's not start that again.
A true benefit of concealed carry laws is that when common citizens commonly carry, lawmen get in the habit of good manners. The arrogance of being the only legal gun in town disappears.