Your post and questions are based on a hypothetical situation where the staff are active shooters and would be criminal shooters are not a threat, which would be a huge problem. Obviously, the risks of school staff shooting a gun at an active mass shooter are less than they would be if a mass shooter was shooting at an unarmed crowd, but in the hypothetical situation that you described where the school staff member is the mass shooter himself, it would be a disaster.
If there was an actual mass shooting taking place inside a school and a school staff member were to fire upon the mass shooter, there would certainly be a risk of harming an innocent student. This risk needs to be compared to the risk of how many more students would be in harm's way if the staff member was not armed, as well as the risk that schools can indeed hire disturbed people who could become the problem mass shooter themselves. Although I am a right winger who is on the side of gun rights, I would need to know that any school staff members who were going to be armed and in a position to defend my child have gone through extensive background checks and firearm training before I would be comfortable having them around my child. I will not automatically discard the risks of arming school staff just because I am a righty, but I can see the potential merits of arming them if the correct training and background checks were done. I am not sold yet, since I am not impressed with how schools are currently selecting their staff.
