In that area of San Diego, there are two types of officers: THe Quick and the Dead. If you are not the first, you will be the second. Information not in news: This guy sat out in his car, taking on liquid courage. By his history, he was probably going to confront and shoot the "estranged " wife. That shooting was hundreds of miles from San Diego, if I am not mistaken, and the officer would more than likely been out of uniform.
As far as confronting the guys wife, that's total speculation, not part of the story.