Killer tadpole?

my neice bought a bullfrog tadpole from the pet store along with 3 mollies [fish] and i feed the tadpole algea disks at night and fish food during the morning [fish and tadpole i guess] and one of the mollies died about a week ago, had no fins and little scales, did the billfrog MURDER him?! lol, but seriously, then today i came home and another one of the fish is dead, again, hardly any scales and no fins. is it cuz the tadpole is hungry or is this natural? cuz i gave him chicken before, and it sat for 2 days untouched. and i overfeed the fish a bit, so there is some at the bottom since tadpoles are particlally scavengers...answer plz!