It seems to be that they are sort of filming some drills, maybe using a bit of archive footage, getting the profile of a “dodgy” character from a given community and then fabricating a scenario well enough that it will convince people that it’s a lone gunmen sympathetic to ISIS – or whatever nonsense they think will work. As the media don’t investigate anything any more and often aren’t allowed to because of “data protection” or “national security,” they can get away with all this.
I think the reason why it is done this way is simply to control the narrative completely. For example, so many people can film stuff with smartphones now and upload it in seconds, they cannot risk a “totally real event” – where, say, a mind-controlled gunmen works alone. In a “real” event, they can’t control what people actually film – 9/11 was a good example of this – i.e. a lot of people filmed the real event and now they are in trouble because the real videos show what actually happened. However, if the only films that exist are of a “staged event,” then they have set up the stage in the first place, so they can control what is on there. The Boston Unbombing was a classic example of setting the stage and building a narrative around it.