Quote Originally Posted by Kurald Galain View Post
The former. When a power is interrupted, you cannot change any choices or parameters of the interrupted power; that's basically the point of having interrupts. So yes, the enemy ends up in the area of his own attack.
Keep in mind that this is only dangerous for the attacker if the power they used has the entry that states "Target: All creatures in the burst/blast". If it says "enemies" or even a specific number (since you can always opt for *fewer* if a specific number is mentioned), swapping positions with the target wouldn't make them get hit by the power because, in the first case, they're not a legal target and, in the second case, they probably won't *choose* to target themself.