It was a requested deletion of the account. I think it started about a year (?) ago where I was forced to allow the deletion of accounts. I don't remember who that is as this isn't the first time I've deleted accounts on request.
Xenforo also implemented something that when an account is deleted, there's an option to rename their username too.
If I deleted his account and it didn't show up as "deleted member #" then either the option to rename the username when deleted wasn't implemented yet or I forgot to select the option to rename the username.
Comments on Profile Post by Svalinn