my condy ate my sailfin?! how? why?

[bv_reefer]

i wake up this morning to see all my fish, including my sailfin tang, all gracefully swimming around, then an hour later at noon i go to turn one of my halides on, when i see this dark thing hanging out of my condy anemone.....my first thought he's dying and all his insides are slowly falling out, but considering his color is same as always and tentacles fully extended that though was quickly ruled out, then i though he's eating my snail, as thats exactly what the dark shape looked like, then i saw the snail; on the other side of the tank. Looked around the tank and on the floor to see if he jumped out, nope, surely enough, my glutton of an amemone made a meal of a once spectacular tang! how? why? what would make him suddenly eat a tang? I even fed him a few days ago!