It would be difficult to overstate Nathan T. Freeman's impact on the Domino community. I can only imagine he was similarly impactful in other parts of his life, but that's how I knew him.
Back when I was first getting involved in Domino, he was one of the main people to follow. I'd read blogs and comments and know that with his name came something very much worth reading. His assertiveness came across clearly, but was immediately followed by the justification.
When I started to get involved in the community, he was the one who brought me into the XPages Skype channel. Over the years, whether it'd be something I did for one of my own projects or something as part of our collaboration on the OpenNTF Domino API, there were plenty of times when I wrote something and thought "man, I bet Nathan will like this". Generally, it was followed by a - quieter - "at least, I hope so".
A couple years back, there was an opening on the OpenNTF board, and I remember that I was talking to Nathan about it at some user-group soirée, and he pitched me on the idea of running for the seat on the premise of "world domination". Though the OpenNTF server-infrastructure plans in question at the time didn't quite rise to that level, you can't fault the ambition.
He aggressively sought to be ahead of the curve, and was more often right than not. He was deep into XPages before most of us, and was out of it similarly early. It's a thoroughly-admirable trait, particularly when paired with the technical acumen to back it up.
I consider myself fortunate to have had the chance to work with him on several occasions, and it's a shame that it was only those few. The community will be lessened for his loss, but we're all a lot better for him having been here.
But there are brass tacks involved here too: his family can use whatever help you can give, and there is a GoFundMe page set up for this purpose. Please, if you can, donate something.