You can laugh, but these are situations where robo-cops can be used. A robo-cop won't be afraid of not doing it's job, and nobody will mourn if the robo-cop gets killed/disabled.
Here's another situation where a human leo arrived in time to very possibly stop some of the killings but waited until all the shooting was done i.e. many kids killed before he acted.
We can criticize AI for taking jobs, but maybe it's time for AIs for a number of police jobs including this one. I have no idea how close we are to having a robot that can effectively simulate an armed leo, but I hope they're close.
Anyway, we use drones now to kill terrorists. Might as well use them to kill/disable bad people here.