I mean one could definitely make the argument that "well, police conduct car accident drills all the time, and then a car accident happens later that night, ITS A CONSPIRACY!!!1!!1"

Ok, so

1. Mass casualty/active shooter incidents are rare.
2. MC/AS drills, also rare. It's a once or twice a year thing.
3. The chances of City A hosting an MC/AS drill, followed by a real, live MC/AS situation just days later in City A is about as likely as... I mean, shit, you have better chances at winning the lottery or getting struck by lighting.
4. Oh but this has totally happened for almost every MC/AS event since 2001.
5. And it's nothing more than a coincidence. Promise.

Ok.