I was watching Fox News with my 5 year-old the other day when Shepard Smith showed a dead body lying on the road. I discussed the disaster with my son and explained what was going on. It was a learning experience and one I think he is better off for. I'm not saying it would be a good idea to pull pictures of bodies off of the internet to show him, but I think it was fine for him to see it in context.
I'm not worried about a one time experience. I'm more worried about a continual replay of the photos. I think that would get disturbing to a child. I think you handled the situation just fine.