Not enough info to make any judgement.
We know witnesses said the dead guy threw a punch at the shooter...but we don't know if the shooter did anything to threaten the dead guy before that.
It does not say the dead guy was armed...so there might not be cause for lethal force. For instance, if the dead guy was 5'1" and weighed 101lbs and the shooter was 6'4" and was a 210 lb martial arts competitor, lethal force might not have been warranted.
The dead guys priors don't have much to do with evaluating his guilt on the day of the encounter. Because he arrested for violent behavior on two occasions in past does not make him guilt of aggressive behavior on this day.....just like if he had a perfectly clean record in the past does not make him not guilty on that day.