Top should have been let to run as you had it on a pully (run off a friction devise, looks like the lower guy was the dude lowering) so as not to shock the tree so bad. Lower guy in the tree could have and should have been on the ground to do the lowering. Both guys could have gaffed out getting hurt. As it was the guy lower I could see when/after the shock hit had his saw all the way out on his saw lanyard that should have been clipped closer to his belt. Could have flipped around that lanyard and nailed his head or something. I know it was not running, but still.... Also could have taken a smaller top section to help lessen the shock.
Anybody want to add anything ?