Yeah, and Clapton himself was almost on that copter (shades of Waylon, right?)
The helicopter was too heavy to take off vertically out of ground effect, so they figured the pilot started forward to gain some translational lift and simply flew it into the ski hill. With the noise of the other copters, no one even knew the crash had happened.
I didn't know the pilot of the accident helicopter, but I knew two guys who piloted two of the other ones. It was kind of agonizing for those guys, but the bottom line is they should have called off the flights and told everyone they would have to drive to Chicago. They really had no business taking off in zero visibility, even IFR - it was the wrong decision.