So what would you call it?
Someone not trained to assist someone who is trained and doing their job, isn't very wise unless it's life or death.
I wouldn't let a person who isn't a law enforcement officer assist me, especially armed. If they want to assist so much, join the force. I don't know them, their intentions, or anything at all.
I asked the OP that I quoted for his reasoning. As I do not know, maybe he was off duty?
Regardless to add. He was with his wife, who most likely was in the line of fire as well. For what? A breaking and entering? Is it that worth it?
Leave it to law enforcement.
And if it was you and your family being shot at and a civilian non leo concealed carrier had a chance to stop the shooter with a single shot you would want him to keep his gun holstered and sneak out of there thereby saving himself and leaving everybody else at risk. I pray I am never in an accident and you are the first one on the scene because you are exactly the kind of guy who would turn his back and leave fearing you might get inconvenienced, your shoes might get soiled and it would take precious minutes of your time to render first aid and call for an ambulance.
Vigilantism is gearing up to punish somebody you assume is a law breaker without benefit of lawmen, judge or jury, you are the sole judge.
A man taking out a spree shooter if he is capable of doing so is a good citizen. Apparently a lot of people find that to be a hard concept to grasp.