You don't know that. It may be, as I said in my previous post, that we just haven't identified an underlying deterministic process, but it also may be that it truly is a random process. If the conventional quantum theory is correct, then then the natural process TRULY is random.
That may not ever change for us humans, but I wouldn't bet against it. Scientific discovery is all about de-randomizing mysterious things and is based on the assumption that nothing is really random, just currently not understood.
Just because we apply random models to processes that we know we don't understand, or to simplify complicated processes, do not let that make you believe that "random" is the same as "not understood".
If there is no such thing as randomness then there can be no free will - because unpredictable living things will create randomness. So then the universe is predetermined.
That is why I ask whether randomness and free will are one and the same... or contribute to each other, or have a common microscopic anscestor, or are related etc...