Atoms and existentialism

When playing pool, if you make a shot there's a set way the balls will react. That is because the balls are made of atoms. As atoms bounce off of one another, they create a chain reaction and they continue to bounce. If you took the same shot over and over, it'd play out the same way. This is thanks to atoms.

So thinking on that, does that mean that from the moment of the big bang, every little detail of earth, the universe, and everything beyond was decided at that point? Seeing as the atoms would eventually bounce in such a way to set it up.

That must mean free agency is a lie. We've never made a decision, physics has already decided what we were going to do.

Or maybe I'm just going mad and in desperate need of sleep