Dear Ruth,
Of course, it's impossible to say with any certainty, but it appears that the convergence of events in a child as sensitive as your son has somewhat overwhelmed him. This is more likely than any one of the variables overriding the others. What would be useful is to chat with him about the situation, noting how sad he appears, and simply letting him talk. Don't try to offer much by way of opinion or even reassurance - just draw him out on what he's thinking.