I'm so sorry to hear of his death, and sending my prayers and wishes for peace and healing to his loved ones.
I interacted with him directly only once, while working on a [buffering-related issue in Open connect](https://gitlab.com/openconnect/openconnect/-/issues/582#note...).
Like many others, I was inspired by his great attention to detail, his diligence, and his curiosity, which served as a fantastic example for many people working on tricky and important issues in networking and other technologies.
Those will be some big shoes to fill.
I appreciate and applaud your inclination to sympathy, but I don't think saying words in your head will help him or his family. Perhaps instead you should let his family know directly that you found inspiration in his work - I imagine they would find that quite comforting in their grief.