[Egon]

Kind of sparse on information. The way I'm reading it is the guy only broke into the apartment because he suspected the resident of child pornography-- maybe didn't realize his sister was a victim.

In a similar circumstance, I might have waited for the guy to come home...

[Little Pig]

I don't see that the burglar actually knew Yearsley was committing crimes. I think he may have known what Yearsley was, and obviously knew WHO he was (this is stated in the article), but to me it looks like he realized, upon finding the pictures, that his target was way worse than anything he might be doing. A similar situation would be breaking into a house to burgalrize it, and finding human body parts, or bombs, and reporting that. Not to mention, the burglar might have seen a way to "erase" some of his past misdeeds by turning in a bigger criminal.