I was very direct with my ds, who is nearly 6. I didn't mention that people had lost their lives, but if he'd asked, I'd have said so (I think).
If I had a more anxious sort of child, I might well have kept it from him, but it seemed the right thing to do for this particular child. (My 2-year-old is happily oblivious.)
I'm not entirely sure I did the right thing, but I'm comfortable enough with my decision.
How did you all handle it with your young children?