Why had he drawn his gun?
As for the self defense, the video also answers that question, showing the car veered away from, not toward, him. Besides, if you're three or four feet in front of a car that starts to move forward it is too late the shoot the driver. The obvious and only self defense is to jump out of the way.
But again, WHY HAD HE DRAWN THE GUN?
He shot and killed her so we can assume that was his purpose in drawing the gun unless there is an intervening event that suggests a different purpose. He claims her attempt to hit him with the car is such a purpose. But the video shows the car was moving away from, not toward him. In addition, two of the shots were fired into the open driver's side window, not the windshield.