So, researching the criteria, we learn that a person becomes eligible for the Purple Heart when one of the following conditions are met and the service member is wounded or killed:
1. In any action against an enemy of the United States.It seems that the only criteria that might apply would be criteria # 6, and I doubt that the Secretary of the Army will recognize this as a terrorist attack.
2. In any action with an opposing armed force of a foreign country in which the Armed Forces of the United States are or have been engaged.
3. While serving with friendly foreign forces engaged in an armed conflict against an opposing armed force in which the United States is not a belligerent party.
4. As a result of an act of any such enemy of opposing armed forces.
5. As the result of an act of any hostile foreign force
6. After 28 March 1973, as a result of an international terrorist attack against the United States or a foreign nation friendly to the United States, recognized as such an attack by the Secretary of the Army, or jointly by the Secretaries of the separate armed services concerned if persons from more than one service are wounded in the attack.
7. After 28 March 1973, as a result of military operations while serving outside the territory of the United States as part of a peacekeeping force.
Those persons eligible for the Purple Heart have my undying gratitude, but I don't think that those killed or wounded at Fort Hood will be eligible for the award.
But, that's just my opinion.