That's very sad. Like many others, I used `cdrecord` and `mkisofs` back in the day.
But mainly I remember him for his work on SCCS. That code was AT&T proprietary for a long time, but it was open-sourced as part of OpenSolaris. Schilling made it portable and produced binaries for several platforms, including the Mac. He even gave some conference talks on this topic. By the time he did that work, most projects had already moved onto other version control systems. But there are older, closed-source histories of various projects (such as Java) that are still in SCCS, and I find his tools useful to this day for investigating those histories.
Condolences to his family.