What happened to the snail on the left?

I found these 2 snails outside of a garden. They were on the wall but they didnt stick there very well. I found 2 snails, i assume both are dead.

One has dust and other stuff in it, nothing too surprising but the other one is what got me really concerned.

Theres dark brown-black liquid inside the snail, and there are also brown-black 4 bugs that looks like one single rice. It also smells horrible.

Any ideas on what might have happened?