On National Public Radio: Trying to discuss the problems with the Gun Violence Archive
1) Media reports rarely cover cases where people use guns defensively. If someone uses a gun defensively and the criminal runs away (as occurs in virtually all defensive gun uses), that is simply not going to be considered newsworthy even if it is reported to the newspaper. If you believe media accounts actually get virtually all the defensive gun uses, you would have to believe that about 85% of the defensive gun uses end in the criminal being killed. No one believes that. It is just that those cases are more newsworthy than cases where the criminal is wounded. Only a few percent of the cases seem to involve cases where no one is harmed.
2) There is no standard reporting for police even when they are told about DGUs. There are no reporting forms for police. Police do not report these cases to the FBI. Justifiable homicides are in theory reported by the police to the FBI, but that data for civilians is even worse than it is for the police, and I suspect you have heard how horribly bad the police data is.