Accidentally killed, I think you meant to say.
It is very easy for those not involved in fire fights to condemn those who are, and whos lives, and that of their comrades, depend on rapid judgement calls.
In the type of conflicts that are occuring world wide nowadays, it is a miracle that many more such incidents do not occur.
The military is, and always has, engaged in "cover-ups" to protect its own from those who have never been under fire and who are quick to point the finger.
The US forces have had more than their fair share of such incidents in the past few years, but then they have also born the brunt of most of the "hostilities" too.
The soldiers concerned in that most unfortunate mistake are also men (and women) like yourselves, and not automatic killing machines.
Think on. And think "There but for the Grace of God, go I"