I worked with him on TruffleRuby for almost six years, and knew him for a few years before that. I think every one who knew him is shocked and saddened by this news.
I'm sorry for your loss then. We followed each other on Twitter and I tried to plug the TruffleRuby and Graal work wherever I could as I really believed it is the future of Ruby. Beyond that what a brilliant writer. This single article helped me understand so much more about a language I've cherished for nearly two decades: https://chrisseaton.com/truffleruby/deoptimizing/