this is kind of old(er) news - local to So Cal. This location is just a couple of miles from where I live - and is a road I drive often - and Sat & Sun AM group rides are ubiquitous in the area.
It happened the weekend before last and got very little play in the news. I've found 3 articles that tell parts of the story - some seem to indicate he was alone, some that he was in a group still - certainly other cyclists were there as they flagged the truck to stop.
I have a theory (though unfounded). I think that perhaps the truck moved a little wide to give more leeway to the peloton (who often ride badly around here on weekends - more than two abreast on shared roads, etc) and that made the trailer move and clip the rider - but who knows. A local tragedy for sure.
Even so, watch out for even concientious drivers on shared roads.
http://www.msnbc.msn.com/id/20 875576/
http://www.ocregister.com/news/ police-saturday-scene-1846313-irvine-julienne
http://www.hbindependent.com/a rticles/2007/09/20/publicsafet y/hbi-julienne20.txt