Stefy Bull, Westgarth's promoter for the fight, also confirmed the death on Twitter. He said Westgarth was "a young man doing a job he loves."
Westgarth's tragic final interview
Westgarth told boxing news site and streaming service Boxing Social after winning the fight: "I think I controlled the fight. He was loading up all the time, throwing big bombs.
"It's hard sometimes, you're going to get caught aren't you? Fair play to Dec, I think it's a good job I've got a good chin really otherwise he would have seen me away.
"He's a good fighter and I can see why he was 11-0. But at the end of the day I wanted it just as much as he wanted it and ultimately I box away all the time.
"I'm used to that pressure whether it's an 11-0 kid, 7-0 kid, I'm not really bothered. I'll box anyone.
"I just enjoy it. I do it for fun, not because I think I'm going to be a world-class fighter. I just do it purely for entertainment and I'm glad we can put on a show and keep everybody entertained."
