Okay, an update.
Talked with my son on Facebook chat an hour ago.
He said that the situation was announced on base by the time he woke up (probably around noon local time because his shift starts at 2pm) so he had definitely heard about it right away. He said that it is essentially business as usual at the base, that there was no heightened alert status ("C'mon, Dad, I'm in a war zone. That's as heightened as it gets."). He also said that the soldier in question did not do this out of Kandahar Air Base but rather from a forward operating base in the vicinity of Kandahar. He did not know the exact location in relation to KAB.
His comments were more than a little comforting to his mother who has been worried sick about him.
That's all that I know at this point.