rear ended claims quite straight forward,... unless the offender did not report to his/her insurance within 24 hr, otherwise it will be a civil claim, which is more tedious.
Do a self claim first, to get the car repaired first
download the youtube video before it gets taken off (may happen).
send the video to your insurance claim at same time, say that the video is from your friend's front car cam.
(try to contact the video sender to explain that you are making a claim, to act as your witness, etc)
Send your front cam video at the same time. (make sure both videos can capture the offender's number plate whenever possible)
any static pics of damage and other car's damage also submit.
your insurance will do the rest of claiming the other party (cross your fingers)
Good luck
