You can pretty much get an idea of a layout of a trailer from standing outside. Especially if you've lived in one before. So when the perp went to the backdoor it was probably because he knew he wouldn't walk right into the bedroom area of the house. So once inside he turns on the light. That does NOT surprise me, nor do I find it odd. Think about it....you're breaking into a house that you're not familiar with, you're trying to be quiet. Which would risk waking someone up more, turning on a light to see, or bumping into furniture and toys in the dark? I'd turn on a light. He was most likely armed somehow so worst case scenario he wakes up an adult and has to kill them to get what he wants....the child. Not out of character considering we're most likely looking at a pedophile and someone that breaks into homes.
Either way this person has balls to do what they did. They don't think about their actions and have no compassion or empathy, Nor do they care about the consequences of their actions. They want what they want and they'll get it no matter what.