Update? did this ever get sorted out?

a few weeks back there was a GoPro video of a group ride on Beach Drive in Rock Creek Park
several cyclists were passing a rider not in the group
that rider motioned to pass... took the initiative to pass
but crashed out the rider behind him and then several following riders

who was at fault?
that is complicated
but for that rider to not stop and check on his fellow cyclists?
that action is in greater question than who is at fault