The guy is under a lot of pressure. I think he knows without a doubt that boy didn't kill all those kids and is worried that if he says so he will be the next victim. He might figure they plan on possibly offing him anyway since they know he knows the truth. It would be interesting to see if his behaviour here is his normal behaviour at press conferences, if he has ever done one before. If it isn't, then I think he has been threatened about what he says to the public.