That's a sad story all the way around. He's only 47 (Yikes, younger than me now!) plus the other guy's going to have to live knowing his friend died putting on a tribute for him...
I wonder if you'll hear what the cause was. Strobe-light induced seizures are indicative of epilepsy, but those aren't fatal unless they occur while doing something more dangerous than playing guitar on stage. Stroke maybe? Hmm...