Oswald, noticing the siren had walked off, had decided to make sure nothing got broken. Or flooded. So he followed the nature-kid and the telekinesis kid around - really he'd need to learn more of their names - because he had learned that really it wasn't a good idea to let kids wander off alone in the woods. Mainly just because they always seemed to cause havoc. 
He caught up to the nature kid, grinning at him. "What do you suppose she's upset about?"