Sorry to hear of his death. I always liked his portrayal of Garibaldi.
Here’s Doyle’s Wiki bio, which has a paragraph on his death: Jerry Doyle - Wikipedia
Sad to hear. I wish there were more detail explaining how they knew this. What did the alcohol do to him that indicated he died from it?
If you like these people, I strongly recommend liking Claudia Christian and Patricia Tallman’s pages on Facebook. They post some good things, including stuff from the show and from recent gatherings. They’re all friends and see each other, and other cast members, on a regular basis with cons and stuff.
Patricia (age 61) posted a pic of herself in a bikini this spring. Still damned good looking.
They may simply be being more circumspect than Thomas Noguchi. William Holden died from alcoholism; it doesn’t really serve us to know that he stumbled, gashed his forehead open and bled to death because he was so intoxicated.
I suspect it’s something like that, if not an internal hemorrhage from cirrhosis or something. Don’t need to know. It was Boozy killed the Beast. 
Similar. He was probably my favorite on the series, and I liked most of the characters/actors on there.