Just the fact that the killer made multiple noise complaints to the police about them lets me know he's not just a cold blooded killer. Or else he woulda done this a long time ago. Seems like he tried for years to handle this without confrontation. But he finally got fed up. This is how quickly things happen. Most shootings happen off impluse and emotions. Plenty of dudes in prison or in the grave right now because they let their egos get the best of em in the heat of the moment.
To me, both of those men were emotionally weak and were immature. These are 40 year olds that were feuding for 6 years over noise complaints. Both of them could have walked away or left shyt alone. One dead, his son dead too and another man about to be incarcerated for the rest of his life.