Despite what I wrote earlier, with the google maps image showing the rumble strips, that shoulder is too narrow for a double pace line. The surface to the right of the tarmac may be "rideable", but not at road bike/paceline speeds. I would be comfortable single file on the shoulder to the right of the rumble strips, but in a big strong group trying to keep a good pace, well....
But even with an escort car, I can't imagine riding 20 mph in a traffic lane of a 75mph highway. That's trusting that all the trucks are going to change lanes in time.
But as
SpeedofLight wrote, we can't understand what happened without some more details emerging. Except that it was a tragedy.