Sounds like there was room for reasonable doubt that he was the one who did the shooting based on the forensics.
Also, it may just be the article using faulty language, but in most states even if the father had shot the man in front of witnesses or admitted to it, immediately following such a traumatic event with no cooling off period, some type of manslaughter would be the correct charge, not murder. So it could be a case where the prosecution tried for too big of a conviction and struck out.
Re: Dad acquitted in killing of driver who killed his sons?
Also, it may just be the article using faulty language, but in most states even if the father had shot the man in front of witnesses or admitted to it, immediately following such a traumatic event with no cooling off period, some type of manslaughter would be the correct charge, not murder. So it could be a case where the prosecution tried for too big of a conviction and struck out.