It is time for our LEO's to be trained and ready to deal with what the terrorists are bringing. I have seen auto weapons in foreign airports and on the streets in foreign cities. It didn't bother me a bit and was almost expected.
If I'm ever at a mass shooting similar to what has been happening recently, the best I will be armed with will be a handgun. I hope the LEO's that are either present or on the way are going to be better prepared to deal with the situation than I will be. If carrying an AR every day is what it takes for the LEO to have the AR at hand when he needs it, then tell him to carry one and give him the training he needs to do it responsibly.
