Basically, to ban that amount of people, he got a console command that bans I'd 1-10000 from Big List O Commands, the t topic of which I will not link.
Please, stop.
Let me get it through your head
Really, stop.
He didn't touch the server console at all, as he didn't need to. He used his one client to send information to the server, which the server accepted.
for(%q=0;%q<1000;%q++){commandToServer('ban','',%q, -1, "Get Rekt");} will actually do the trick.