Hi OP,
I can understand why you are worried.
If he's seen the video/photos and is sure it's him then it's a different ball game.
It's good he's contacted the police.
Do you know how the blackmailers have contacted him?
The fact they've threatened to release the footage to his social media contacts means it's also vital he get in touch with the company owning the platforms he uses.
For example here's the link to the Facebook report form specifically for "sexpolitation".
m.facebook.com/help/contact/567360146613371
All reputable platforms have similar.
The main thing is not to respond directly to the blackmailer.
As a pp said they want an easy target. If you pay they WILL come back for more.
From a risk point of you you are best off heading this off now. Remember he will feel he's the only person they are targeting but sadly there will be hundreds if not thousands so that buys time to step up with the police and SM companies.
Yes there's a risk the footage will be released but that's true even if he pays up.
He needs to think about what he'll do.
If he's already contacted the SM companies they will help "clean up" the comms.
Ultimately he can style it out or say the footage is fake.
Either way people who are real friends/family will delete it and be supportive.
Good luck.