Someone hacked into my Realm

My friends and I were playing in my Realm earlier, and someone hacked in, removed all of our belongings, and killed us.

Based on the chat, the hacker had the Profile name of "monjang"

He is not a player in my Realm.

Could you please check the record and help me to resolve this issue. My friends and I do not want strangers hacking into our realm while we're playing.

Thank you very much.