In my opinion, "other things are just as bad" is as good an argument as "if you turn it off, it's not dangerous".
I still think it's not smart to send push notifications in an active shooter situation for a feature that is made to give people who are not involved peace of mind. If you consider such risks, and not get defensive right away, you will find that solutions can be pretty simple, e.g. a banner inside the app, instead of a notification.
I think shooting was aready over before people over at Facebook even knew something is going on. I imagine they wouldn't even turn it on before the information hit mainstream news.
I still think it's not smart to send push notifications in an active shooter situation for a feature that is made to give people who are not involved peace of mind. If you consider such risks, and not get defensive right away, you will find that solutions can be pretty simple, e.g. a banner inside the app, instead of a notification.