More information can be found in the News Gazette article on the accident. Ash was a Professor Emeritus of Mathematics at the University of Illinois at Urbana-Champaign. Longtime colleague Michael Pursley remembers Prof. Ash:

During the period that I was at Illinois, Bob Ash spent most of his time teaching (which he did very well), jogging, and writing books.  Most of us know him as the author of one of the early textbooks on information theory, but that was just the start for Bob.  He always seemed to master new concepts very quickly. One week he would tell me that he was learning a new subject and by the next week he was writing a book on the subject. 

Ash was the author of many textbooks (including an early book on Information Theory). He posted many of his books as free downloads on his website