Assuming he's truthful that he was fearful of attack by the terrorists, it seems to me the more proper charge would be disregarding standing orders and SOP's.
He was committing a felony, and people died when they weren't supposed to. That's "felony murder" right there.
Assuming he's truthful that he was fearful of attack by the terrorists,
Said fear having been caused solely by his own irresponsible actions.
it seems to me the more proper charge would be disregarding standing orders and SOP's.
Which amount to committing a felony, and the deaths directly consequent to committing said felony become two counts of murder.
This, by the way, is why you have a right to remain silent.