someone please help me

Today I came home with 2 less neon tetras. All I found was a piece of flesh my the filter. I started with 5 now I only have 2. I have all friendly other fish in my 30 gallon tank. 3 cory catfishes, 1 adult female guppy and 5 baby guppies. One adult platy and then one baby platy both females. The...