They definitely do get killed by tomatoes, but you might be experiencing a very subtle bug i found and fixed after the jam went live. The bug is that mice don't "die" until after they can play the death animation, which is getting stalled by other animations. so you'll see them die inbetween a) attacking or b) getting hit in the game jam version. I fixed it already for post jam though, as surprisingly it wasn't impacting too much based on comments. Thanks for playing! :)