So mad right now GRRRRRR!!!! (R.I.P. froggy)

[naesco]

I have never kept either a lion or frog fish because I am not into predators.
When you have two fish in a small tank these attacks are likely to happen.
http://www.wetwebmedia.com/dendrochirus.htm recommends a minimum 40 gallon tank.

I know you are familiar with this site. Any reason you didn't check this out before you bought the fish?
You will need to rehome at least one of them if you you want the frogfish to live IMO.