It's Kira seems to think it's his.
Bites The Dust kills whoever the boy feeds information to, then rewinds time by 1hr - erasing any deaths or events that happened during that time. The teapot set is intact, for example.
The weird thing is that if you're rewinding time, you really don't need to kill. Blowing people up fits with his theme, but rewinding really doesn't.
I see where you're coming from, and perhaps the boy rewinded time by 1hr just to save himself. The aspects against this idea though is that the boy hasn't been hit by the arrow yet. It's also somewhat reasonable for Kira to not know about the rewinds because the power is automated, just as he doesn't actually know what his tracking bomb is up to. He just assumes it does its work.