TO be serious,
The old man actually have did nothing wrong although you may get attention to his shacking hands.
Look the video carefully,
You can see that the young ppl in Grey color is to be blame(responsibility 70%).
he suddenly drive his bike to right without any hand sign.
Also , his firend is also needed to be blame (responsibility 20%)
How come you guys occupied both side of the road, that's mean you force ppl to pass you 2 at your middle.
It is not banned to ride bike in parallel, but please do it at 1 side only.
Finally, the old man crashed only because he has not ring his bell, not because he shake his hand (so only 10% responsibility).
I hope some ppl can help to explain the real reason to that 2 young people.