No crime was stopped because the guard shot the subject. However...FURTHER criminal action was stopped decisively.
The act of entering a business or residence armed with intent to commit a crime is, in fact, a crime. If the subject happened to have an accomplice outside scuh as a driver...that is conspiracy. Boom...felony right there.
The subject was armed, demanding money, or drugs, or both. We can see the pharmacist clearly offering him a bottle of pills. The pharmacist, and the woman who I assume was his pharmacy tech, were both cooperating.
I am going to go on the assumption here that the retired officer, since he had his ass in the grass so to speak,reasobably knew the subject was capable of following through on whatever violent threats he may have made. This is a reasonable assumption because a reasonble man would believe that an armed criminal making threats with the ability to carry out that deadly threat, i.e. a presumably loaded pistol, would shoot them.
In this day and age, robberies are far more likely to end in a clerk, business owner, or innocent bystander being shot or killed by the subject, than even 10 years ago. Gangbangers and prospest gangbangers looking to get "jumped" into their gangs are often jumped in by having to commit a violent crime or random murder than ever before. To my reasonable frame of mind...an armed subject is probably going to shoot someone in the commission of his/her crime.
The guard/retired officer had years of training and street savvy in his toolbox. He was equipped to deal with the threat, and he did. Sure, in a rosy, huggy, touchy feely world, he could have talked the subject out of his crime and bought him a latte afterward, and explained it wasn't his fault that he had a crappy childhood, or didn't get enough hugs when he was growing up. But, since it isn't a rosy, huggy, touchy feely world, the guard/retired officer used his tools, experience and training to prevent the further crime of murder, or attempted murder.
The subject CHOSE to rob that store. He CHOSE to threaten innocent lives. He CHOSE to accept whatever consequences of his actions were. In the end, he CHOSE to die. The owner of the store CHOSE not to be a victim, and hired someone to protect him and his employees.
I feel bad for the guard/retired officer for having to take a life. I feel bad for the pharmacist and his tech for having been traumatized by their part in the incident. On the other hand...they are alive, and can heal.