Someone is making multiple accounts to harass me

So I keep getting a user who is constantly adding me and harassing me. I have blocked the first few but they just keep making new accounts and are constantly trying to add me. The only reason why I know its the same person is because its the same user name but they'll but accents or numbers in front to change it up. What to do I do? They have been sending me death threats, if I send a ticket wouldn't it only be banning that certain account? Please help.