Idk i think you at least need to tell your child that bad people exist. Not doing so may be doing them a disservice in the world. My husbands very angry at his hometown for sheltering him so much because he never learned about anything real which hurt him a lottt down the line. I understand not wanting to explain the active shooter part. Maybe phrase it as like a robber in the game cops and robbers or something simpler. But they NEED to know sadly. Assuming you’re in America, its almost a necessity you explain how they should react if a “bad” person is around because the bad person part is almost inevitable at this point. The country is a mess :/ I’m sorry