Here’s an accident with a happy ending:
May yours come out as well.
In the vid it seems like their front end was undamaged. I hope that implies that your rear end damage is relatively slight & cosmetic.
I tried to see if I could tell whether the other driver was face-down in their phone. Couldn’t tell. Damn.
I assume your cameras also recorded the front view. Which would be important to establish why you stopped at what in the rear view appears to just be a random spot in the road.
To be sure, the rule of thumb is that a rear-end crash is always the fault of the following car. But there are exceptions. Not that this is one of those situations, but it’s sure what the other side will claim.