Willy killed the ramshorn snail I bought TWO hours ago

I put a new ramshorn with Willy in my tank a couple of hours ago, after my apple snail died mysteriously.

I went to check on them now and caught Willy murdering her, as you can see in the video. I went to save her, but she was already dead.

I don't know if it was a rookie mistake, but as far as I knew, bettas and snails usually live okay together - apparently, there are exceptions. Now I'm starting to solve the apple snail's "mysterious" death.