*spoilers* Picture Explanation

The reason he took the pictures is kinda of vague but I think I can help with this...in the beginning he is lying a bit here and there (about the dog and this and that), trying to make sure he wasnt a suspect at all (eventhough we all know he didn't do it). So During the course of the interrogation he says that Chantel can't have children when confronted by the fact that he has none. We later find out this is a lie. I firmly believe that he is the one who can't have children and he is embarrased of that fact that he cant have children thus he lies about that fact. He so desperatly wants children though and in his desperation he takes pictures of children to fill the void in his life that will never be filled because he can never have children.