Hacker Caught!

So once I Joined this server called ''UltimatePvP''. But then,when I saw My inventory You got to start with 2 stacks of diamonds and 2 stacks of obsidian I was excited because I could make Some diamond armour.So when I got out to wilderness, I Made a faction called ''Cheesy''.After that, I made a small obsidian base and claimed it,When I came spawn I forgot to make some diamond armour to Kill some People.I came back spawn I Made friends with a few people and allied them so we could kill some people and not accidently hit each other.Then This guy Called Romeio26 Said ''Cheesy faction=Raided'' I Obviously thought he was Joking.But when I came to check he was Somehow in My base when it was claimed.Then he killed me with his fire aspect sword.I didn't know how he came in.