Google Translate says
"How can it be that Russian players attack and ignite an enemy castle with a shield?
Something has to be done here against cheaters."
This should not be possible. You should lodge a ticket with Plarium showing screenshots/video of this happening.
Dies sollte nicht möglich sein. Sie sollten ein Ticket bei Plarium einreichen, das Screenshots / Videos von diesem Ereignis zeigt.
The situation is this.
The time its takes for the competition to end, and everyone lingering to be sent back home seems to vary from competition to competition.
Whilst there, there is nothing presently to stop these kinds of hits, and of course it can be construed that its pretty mean spirited to do this kind of thing, but is it?
It's easy enough to take whatever advantage you can get from still being in the enemy kingdom and to think might as well.
Why your particular situation happened is something thing that only the techs can answer or fix.
Though I can point out towns are known to be caught in the enemy kingdom, and this might be why your attacker was showing as belonging there.
If you are stuck in this situation and cannot do anything about it all the player can do is the usual ,wherever that might be.