In the END he is responsible for his actions. However, completely? As if you've never been so angry you've never yelled out? Broken anything? Etc? When we lose control of our emotions we aren't thinking clearly. It's not an excuse. it's simply a reason. I can't contemplate the weight of what this kids emotional state had on how much premeditated murder took place or whether he thought he was being a big man, suicidal, or whatever he may have had in mind right that minute. Who knows. But, really. Only a simpleton blames the bear crossing the road when it gets hit by a car.