The fact that the weapon misfired may open a brief window, however, the shooter had a shotgun slung and two sidearms as well. As for saying how one would react in such a situation, that kind of conjecture is as vague as the shot you would be presented with. Nobody knows what they would do in such a scenario until they actually find themselves in it. Another factor is the presence of your family. I'd be far less likely to attract the shooters attention if my wife and kids were sitting next to me. If I was alone, I most likely would return fire, but then again, I get paid to carry a gun, and can assess the tactical advantages/disadvantages of engaging. If there was a moment or position of advantage to capitalize on, I may take it. If not, then I'd most likely take cover and try and use the shooter's position and targeting to make my escape. The average citizen would not be able to assess the target and would probably jump out at an inopportune time, guns blazing, and either be mowed down, or would creata a very dangerous stand off. Even with training, I have no delusions that I would probably die in such a skirmish.