It's your fault for giving him op.

Though I paid for a global and stuff.

Still your fault.
Give op to only those who you completely trust.
Whatever happens after that is your own business.

If you pay for a global the only one that should be op in that server is you.

Your fault for trusting a kid like that.

Giving someone OP is like handing over the server ownership with it.
Regardless of if you actually paid for the global or not, the person you OPped is allowed to de-op you under any circumstances. He's allowed to do anything you are with the OP.

Next time, don't OP people unless you're sure that they will respect the original OP.
Set an owner pass (/set owner [pass]) to ensure the protection of your server up another level.
Closed - PM me if you have any questions.