How should I fix this situation?

Hello,
I have a terrible situation where there was a bit of leaking occuring in the ceiling from an unknown origin.
A little later, in our shower, the tiles seemed to be not solidly in place as if I added a bit of pressure, the tiles would push in. Then soon after the tiles gave out and now there is basically a big hole in the shower wall where the tiles caved in. I am not sure how any of this stuff works, but I thought there would be solid wall behind all of the tiles.
I think we have mold but I cannot tell.
I put a plastic covering over it with duck tape as to prevent water from getting in.
Please help! What should I do?