The Old Wizard was utterly confounded.
The person standing before him was his most prideful student, who, after studying with him for many years and going out into the world, returned only to unleash a catastrophic attack upon him.
He couldn't understand how the other had suddenly acquired such immense power, nor could he understand why they would do such a thing.
Facing the Old Wizard's confusion, the green-haired youth spoke, "My dear teacher, in truth, I haven't betrayed you. The reason I struck you was merely to save you. Yes, to save you. Do you know, your research is mistaken, and you have embarked on a path that will never succeed, sinking deeper and deeper.
As your student, I couldn't watch you continue to err, so I could only endure the pain of killing you, to end all of this myself. If, after death, your soul still exists, someday, you will understand my earnest intentions."