I thought about starting this thread myself when I heard yesterday, but I wasn't sure enough BC'ers would know who he was.
I first saw Twisted Sister on The Tube in 1982. Then on Top of the Pops with 'I am I'm me', and that was it, hooked for life. My top 3 gigs are all Twisted Sister gigs.
55 years old, that's no age these days. Cause of death doesn't seem to have been reported yet.