/sci/ - Science & Math

Comp-Sci friend here. I've just finished my math minor recs by taking some data science and machine learning courses offered by my math department and I loved them so I wanted to learn the mathematics behind it all. Unfortunately, I haven't taken a transition to upper math course so I can't continue taking "real" stats classes. Anyone have autodidact friendly recs for online courses or books for mathematical statistics?
Picrel is the book I used for my courses. Interesting, but almost all of the math is stripped out, basically zero proofs.