ALICE drill resources for first graders?

Hi parents - I'm sure a lot of you are familiar with ALICE drills. Happily for me I was a kid in the 90s and early 00s and I've never had to sit through one but I just got a note from my first graders teacher that the school had one today. He's my oldest and this is my first foray into this arena. I'm heartbroken for him, obviously, as I'm sure we all are when we have these moments when we have to confront reality with our small kids. Anyway. Just two nights ago at bedtime he was telling me he was feeling scared bc they had a fire drill at school and the alarms are so loud. We had a good chat about how loud noises are scary but they're there to keep you safe and make sure that you could not possibly miss the alert. But now I'm in uncharted territory. Any resources or thoughts on how to talk to my sensitive kid about this this afternoon? I know the school will debrief, and our local PD is there today walking them through it so I don't think anyone is doing a bad job at all, I just know he's going to come home nervous and I have never crossed this bridge before. How can I reassure him that school is safe.. when this drill flies in the face of that statement? Ugh. Any books, shows, stories... Whatever you've got that's age appropriate for 1st grade. Thanks fellow parents 💛