As a parent of 3 children, I can only speak on how I would feel if something like this were to happen to my family. When a child is kidnapped or is reported missing, you would definitely want to be as open as possible with everyone in involved, including the media. But you would still be responsible for protecting the other children in your family as well, especially when we are talking about young minors.
In this case, we have a murder. There is no question about the wherabout of little Leila, unfortunately. So while there is interest in apprehending the killer and getting him or her off the streets as soon as possible, it is even more vital to the parents to protect their remaining children as much as possible, especially the 12 year old brother. If you were a parent that just lost a child in such a horrific manner and your son was the person that was at the scene, trust me-you would do EVERYTHING in your power to protect your child over anything else. Of course, you would cooperate with LE, as it has been indicated that they have in this case. But beyond that, they owe nothing to the general public. This boy and his siblings have suffered a tremendous loss and nothing will be served by poking into their private family life at this time.
Just my opinion, thankfully, as I have never nor do I hope I never have anything like this happen to my family.