I know folks are critical of the cops for not checking the cars. Got it. I would take a slightly different perspective on that. They can't check everywhere all the time and I have never seen a vid where the cops check every nook and cranny, vehicle, treehouse, shed, etc.
Personally, I would not choose the word critical. There were obvious mistakes made that police themselves are sure to point out to future trainees or as a review into the shooting.
The fact is that training only go's so far in assuring Police make the right choices in a given scenario.
What appears obvious was that the first three Officers that showed up appeared to have had tunnel vision. No one appeared to be looking out for outside threats like flank or 6 o'clock.
Situational awareness when approaching a home even for a knock and talk, is standard protocol, and for at least one officer to check for outside threats.
Anytime there is even two officers that show up at a home, notice how one will engage in the conversation while the other stays back observing. They will look left and right and at the person holding the conversation. They are looking for possible threats, for someone approaching, etc.
If you have never seen it, watch an episode or two of COPS. Observe how they approach a home or a person when they are attempting to communicate with someone for information or details to an event.
Even if they had covered their flanks, they still may have missed the guy in the car, but more likely they would have seen him than not IMO.