tragedy, adding it would not appropriate for the coalition to comment further while the investigation is under way. the u.s. wouldn't comment on the origins of the bomb, but the state department is calming for a saudi-led investigation which the u.s. defense secretary supports. >> wars are always tragic, but we've got to find a way to protect incidents in this one. >> reporter: osama's cell phone footage is all he has of the two boys, their last happy moments. osama's father is optimistic the investigation will change anything. in a country where loss has become common place, they aren't even praying for justice anymore, just peace. cnn, london. earlier i spoke we are tired u.s. air force lt. col. rick