If your friend can’t get into their account because it was taken over by someone else, please ask them to refer to the article of You think your account was hacked or someone is using it without your permission.
If your friend is medically incapacitated and unable to use Facebook, Facebook might be able to help you remove their account. If your friend’s condition is reversible, Facebook can deactivate the account instead of deleting it. That way, when this person recovers they can log back in and reopen the account.
If your friend passed away, please report their profile to be memorialized. Memorializing an account helps keep it secure by preventing anyone from logging into it.
Learn how to keep your Facebook account secure so as to prevent being hacked.
Source: https://www.facebook.com/help/162166840513454?helpref=uf_permalink