The horrific killing spree committed by Jerad and Amanda Miller in Las Vegas leaves many people wondering what happened and how the tragedy could have been prevented. While we may never have all the answers, the details of the case do call into question to idea that the way to stop a bad guy with a gun is by having a bunch of good guys with guns in position to shoot the bad guys with guns. In reality, most active shooter situations are ended on the shooter's terms, often by the shooter taking his (or her) own life.
In the Vegas incident, five people died. All five were armed at the time they were killed. The two perpetrators (Jerad and Amanda Miller) were armed as were all three victims--two police officers and an armed civilian who attempted to stop the killing spree, but was gunned down by Amanda Miller. That victim, Joseph Wilcox, tried to be Wayne LaPierre's proverbial "good guy with a gun". While his efforts were indeed heroic, they were ultimately unsuccessful, because as he tried to kill one murderer he was unaware that another murderer had already drawn him into her gun sights.
The problem with the "good guy with a gun" taking down a "bad guy with a gun" solution is that the element of surprise unfortunately usually favors the "bad guy". For this reason, citizens attempting to respond to an active shooter situation are seldom able to sort through the chaos to assess the situation and react in a timely fashion to neutralize the threat. The "bad guy with the gun" usually has already devised a plan and is in a much better position to get off the first shot in the event of a mutually armed encounter. Jerad and Amanda Miller were able to execute two police officers and an armed civilian, because they ambushed them. While we can acknowledge the heroic efforts of Joseph Wilcox and the two slain police officers, it is hard to argue that arming the good guys would have prevented the carnage in Vegas, since all of the good guys were armed when they were killed.