They could, if they had that information. I have meetings scheduled out until November right now. If I tell you I have a meeting on Monday and here's the agenda for the meeting, that's releasing the information before the event happens.
Plans can change, the past cannot. Now, if there's breaking news however and it affect a large amount of people in a negative way, you'll notice it'll be reversed before it'll become finalized. This is something similar to that vein of thought, and IMO is why social media is important.
I'm trying to wrap my head around just what wikileaks is doing differently here, regarding BEFORE and AFTER. It would have been nice if wikileaks had told those photojournalists that the gunship was coming BEFORE they were killed, instead of posting the video of the event AFTER it happened.