Who did it- brigg snail deathes?

So, one of my little fishie friends either killed, or pestered to death two of my briggs snails- and then, the snail carcasses, became the favorite tank snack.

Tank occupants at the time of the incident:

-Cherry shrimp
-Male and female endlers
-Amano shrimp
-Corydoras aeneus
-Lone gold tetra (used to have a school- he's the only one left, but seems to latch on to the cories- though perhaps I should bring him to a pet store where he can have friends of his own kind)
-Baby mollies (less than 1 inch long)
-L-144 ancistrus
-otos

The tank also has or had MTS, though upon inspection- I am not sure there are too many left- I see some empty shells. Certainly not the plethora I've come to expect.

Any thoughts as to what may have happened?

bump, anyone?

I don't want to get more brigs until I figure out who caused their deathes.

Thanks for the responses.

I've actually only had these for a month or so and they were supposed to be juvies, but perhaps the seller was mistaken.

I'm thinking Snoopy might be right- I did notice them being groomed by the shrimp, but didn't realize it would be bothersome for them. I did notice that one of them was closed up a lot.

I'm having bad luck with snails lately- I lost two nerites in my betta/frog tank, as well as these briggs. Fortunately, my other 5 nerites are doing very well.

I'm not sure about the MTS though. I'm going to some more poking around during this evening's water change.

I have used Jungle Ich Guard, about a year ago, but that is it. The tank was taken down, cleaned out, and then set-up again with new substrate since then.

If it was a residual medicine problem, should this affect the shrimp as well as the snails?