I could be wrong, but didn't promoter Bill Graham (the guy largely responsible for booking these bands at the Fillmore) die in the same helicopter crash as Stevie Ray Vaughn?
Both quotes below are copied and pasted from Wikipedia.
Graham was killed in a helicopter crash near Vallejo, California on October 25, 1991 while returning home from a Huey Lewis and the News concert.
On August 26, 1990, a sold out concert of 30,000 in Alpine Valley, Wisconsin featured an encore jam with Vaughan, Eric Clapton, Buddy Guy, Jimmie Vaughan and Robert Cray. On August 27, shortly before 1 a.m., a helicopter carrying Vaughan en route to Chicago crashed within seconds after takeoff.
