He was angry cuz the Army wouldn’t permit him time off to go to his mom’s funeral.
NOTHING to do with combat strees.
He was angry at the US Army, and this is how he showed it.
It is virtually unheard of for a military member to be denied emergency leave when there is a death in the family, unless they are in some sort of trouble, or the doctors were concerned that he might be a threat to himself, or others.
Eventually, the Army gave him a 24-hour pass. Not much time to get to the funeral, bury your mom and return to Fort Hood. He was obviously on a fairly tight leash—but they haven’t said why.