He was also known as law professor Dr. Frederick Dennis Greene of the University of Dayton, not the former NFL and college football coach. He died after a brief illness at age 66. Greene left Sha Na Na in 1984, returned to school, and began a career in law, and also had been an executive at Columbia Pictures. Most of the original members of Sha Na Na (two of them are still with the band), went onto distinguished careers in law, medicine or academia.
http://variety.com/2015/music/obituaries-people-news/dennis-greene-dead-sha-na-na-dies-1201590284/
http://variety.com/2015/music/obituaries-people-news/dennis-greene-dead-sha-na-na-dies-1201590284/