I probably read about two or three of these a year, at least, of some citizen defender, lawfully carrying a firearm, coming to the aid of Law Enforcement.
It's not uncommon for LEO's to be ambushed or even outgunned by threats and Citizen Defenders can play an important role in getting bad guys to retreat.
Here's just one more example:
http://www.foxnews.com/us/2018/02/04/man-carrying-concealed-pistol-stops-attack-on-utah-police-officer.html
