The FBI tracks active shooting cases-where individuals attempt to kill people in public places, excluding those tied to robberies or gang violence. This study is the first to systematically compare how uniformed police and civilians with concealed handgun permits perform in stopping these attacks. Civilians with permits stopped the attacks more frequently and faced a lower risk of being killed or injured than police. Officers who intervened during the attacks were far more likely to be killed or injured than those who apprehended the attackers later.

It seems to me with the US administration in its current form, it is not possible to trust material emitted by FBI.

Also, thought crosses my mind, given how forward police are, if there was an active shooter, and I myself was in area with my own weapon, I would be extremely concerned about being myself shot by police.

In any event, whole problem exists only because of private firearm ownership. Remove that, start very long process of disarming civil society, which also in end leads to disarmament of police. In UK, police do not carry guns.

Don’t forget active shooters are armer civilians too