Sad story, but if he is going to take the rap for a murder charge, he could of at least finished the job thoroughly.
What if he had run out to the street in an attempt to stop the perpetrators, keep them there until the police arrived. By getting in front of the vehicle and telling them to stop. Then, as they continue to drive away, they were obviously attempting to run him over. He fired in self defense... The police use that one all the time.