Damn. Hans was the primary person responsible for Infiniband in FreeBSD, and also the Mellanox ethernet drivers that made their way into FreeNAS/TrueNAS.
That's very sad. Remember seeing that last name Selasky in the kernel source code. I definitely appreciated his ISDN support 25 years ago in FreeBSD - a life saver. And all the other amazing contributions. What a loss.
I have used his ISDN stack thoroughly, implementing call-logging with a client for workstations linking the call directly to a CRM and voicemail. I remember him starting his alternative(?) USB stack. I also contributed an addition to an existing driver importing a hand full of Linux drivers for small peripheral I2C chips. In hindsight this path must have been inspired by his previous work.
Super sad to see him go this young, and it amazes me to realize how young he was when he was contributing all this heavy lifting already.
I remember Hans from his work to integrate the Video4Linux libraries into FreeBSD. He was a very gentle person I enjoyed to work with. I will miss him.