I dunno. It sucks that those guys were gunned down while defenseless. But whatever terrorist leanings Maj. Dipshit had, he was an Army Officer at the time of the shooting. Which means this is, kinda by definition, a friendly fire incident. About which and PH's AR 600-8-22 says:
(8) Members killed or wounded in action by friendly fire. In accordance with 10 USC 1129 for award of the Purple Heart, the Secretary of the Army will treat a member of the Armed Forces described in (a), below, in the same manner as a member who is killed or wounded in action as the result of an act of an enemy of the United States.
PH's are awarded to (Same ref):
The Purple Heart is awarded in the name of the President of the United States and per 10 USC 1131, effective 19
May 1998, is limited to members of the Armed Forces of the United States who, while serving under component
authority in any capacity with one of the U.S. Armed Services after 5 April 1917, has been wounded or killed, or who
has died or may hereafter die after being wounded—
(1) In any action against an enemy of the United States.
The PH is pretty clearly a
combat award.* All the various ways to earn it involve being in action. I'm not sure that being murdered at home, by anyone, counts as "in action". Sucks for them, but there it is.
Related note: Did the victims of the Ft. Bragg sniper get PH's?
*On the flip side, we hand out participation Bronze Stars now, so what does it really matter?