Shrimp Killer

[Aquattro]

I also just drop my shrimp in, no problems. I would suspect a mantis too, as they seem to be able to more easily get shrimp. Hermits are tough, I've never lost one to a mantis. I had a mantis banging on a snail the other day, no luck there for mantis either. Luckily I saw it and it was in a small isolated rock, which is now in quarantine in the backyard.
I've discovered new mantis and crabs in my tanks after years of running, so it is possible to have a long running tank and still miss stuff.
It could also be the 6 line, but you'd probably notice aggresion as soon as it saw the shrimp, not in the middle of the night.