All of these things are suggested, but they are not the main thread of the story and this makes the film feel more "real" than the amateur documentary work shot by Brian that is woven into the film. All of these plot intimations may well be true, might have happened, but any future which might have been is lost in a blood-stained alley. We don't know where their work may have lead, because their work is irreversibly ended. What is often a late second act scene of a regular buddy movie is the point where this film stops. The story doesn't end, it is stopped, and this is handled deftly by David Ayers' team.
As I said earlier, the camera gimmicks in this film mostly got in the way of the story. The perspective didn't add much to the scenes, and often clashed with more polished filmmaking elsewhere. This isn't really shot "documentary style"; this is a narrative film which incorporates verite formal elements. The Paranormal Activity films follow the same form, and no one would say they look like documentaries. Besides, the only footage that Brian shoots (as opposed to the vest cam he's rigged up) is of him and Mike goofing around the station or in their squad. He's not doing hard-nosed journalism. There are few moments when the POV is effective, one of these a brief but intense shoot-out captured by dash cam.
Jake Gyllenhaal does a lot of work bringing Brian to life. There is a sense of authenticity to him, and much of his backstory can be deduced by the subtleties of his performance. I knew he had been a marine long before this was mentioned in the film. Mike is strangely out of place, though. He's played as an eager young cop, perhaps more green than Brian, and somehow less in touch with the citizens around them. There are moments where this becomes a point of plot, but it's not a point made strong enough to explain why it's so prevalent in the movie.