Yeah. People tend to forget that all shrimp and crayfish are opportunistic feeders. Yes, they are mostly scavenging types... but I've seen a 1.5-inch crayfish take down a 2 inch female betta, drag her into it's little cave under a rock in the tank, kill and eat her. It took her while she was resting or asleep, I'm guessing. So yeah, this information doesn't surprise me and I've never kept ghost shrimp or any invertebrate for anything but food ever since.
