WOW! This might explain my experience with shrimp.
For a while my 10 gallon was empty except for some ghost shrimp. I was moving fish into the 29 gallon which was new at the time, this was quite some time ago.
Everything had been moved over for about a week, so I went and bought 5 neon tetra. (the tank was quite boring with just shrimp) I floated the bag and then released them. The lights were off and I left the room for a while (I don't remember now what I was doing) I came back maybe 20 minutes later and one of my ghost shrimp was swimming around with a dead, almost totally consumed neon.
I gave the shrimp the benefit of the doubt- maybe the neon dropped dead right away and they picked him up
Now, I really wonder
After that, they just hogged all the food and such, it took a special method to feed the neons.
All of a sudden, the shrimp just started dying, maybe they were old or something. As you can imagine, I was heartbroken over the death of the shrimp. Not! Actually, I was kind of glad they died- I felt bad, though. The neons were much happier once the shrimp died.
These were regular ghost shrimp- were about 2 inches long, I had them for a long time.