Premise: Glenn Martin Christopher Francis Quinn (May 28, 1970 – December 3, 2002) was an Irish actor in television and film, known for playing Mark Healy in the American sitcom "Roseanne", and Doyle, a half-demon, on "Angel", a spin-off series of "Buffy the Vampire Slayer".
Hypothesis: Glenn Martin Christopher Francis Quinn was in his 40s when he died.