According to the article, a Humvee accident was the cause. Kelly was traveling with the Army's 3rd Infantry Division. Searching on the WP's site reveals that one soldier also died in the accident.
I will hold back any snarky comments I might make about Kelly's politics, and simply say this: like everyone else who's died in this invasion, on both sides, I wish it could have been avoided.
"Let me put it another way. In support of our troops, I recently offered one of my angry correspondents on this issue a bet: I will try my damnedest to keep her son out of combat in the Gulf, and she will continue to support the president's war drive. Whoever keeps her son alive longest, wins." -- Ben Tripp, CounterPunch