Clearly not self-defense. As a general rule, one must apply the concept of ability, opportunity, and jeopardy before the use of deadly force is an acceptable option. Did the deceased have the ability to hurt the defendant? Did he have a weapon of any type? No indication that he did. Did he have the opportunity? Perhaps since he was moving towards the defendant. Was he placing the defendant in jeopardy? No indications that he was. So the defendant is charged with murder because he killed somebody that was not a direct or immediate threat to himself.