“Put your gun down!” someone shouted in the middle of a protest in Ferguson, Missouri, on Tuesday night. The man holding the gun was a police officer; he was walking toward a group of protesters with a raised rifle, which he pointed at them. None of the people in the crowd, as far as anyone can tell, had guns of their own. A few of them had cameras, including one person who, as Mashable reported, was narrating a live stream on the site Ustream. The video shows the officer with his rifle raised and ready, pivoting this way and that:

OFFICER: I’m going to fucking kill you! Get back, get back. VOICE IN CROWD: You’re going to kill him. OFFICER: Get back! VOICE: What’s your name, sir? OFFICER: Go fuck yourself! VOICE IN CROWD: Your name’s “Go Fuck Yourself”? All right, Go Fuck Yourself. Hello, Officer Go Fuck Yourself.

Even before the exchange, the police officer looks on edge, disoriented, almost frantic, and, most worryingly, entirely prepared to shoot. Another officer seems to recognize this, and calms him down and leads him away. His superiors also seem to have realized that he crossed the line: soon after the A.C.L.U. sent a letter to the Missouri Highway Patrol, on Wednesday, complaining about the incident, the organization was told that the officer would no longer be deployed in Ferguson.

In the eleven days since Michael Brown was shot and killed, we’ve been reminded of the many things that are not illegal (recording police actions) or, if they are, do not carry a death penalty (stealing cigarillos, jaywalking). Cursing police officers is on both of those lists. In an opinion piece in the Washington Post this week, an officer named Sunil Dutta wrote that the way to prevent police shootings is simply for people to show more respect for police authority. (“Even though it might sound harsh and impolitic, here is the bottom line: if you don’t want to get shot, tased, pepper-sprayed, struck with a baton or thrown to the ground, just do what I tell you. Don’t argue with me, don’t call me names, don’t tell me that I can’t stop you, don’t say I’m a racist pig, don’t threaten that you’ll sue me and take away my badge.”) That is not how it’s supposed to work, in this country, anyway. We respect the police as professionals because their job is so hard, and so important; it can involve chaotic nights and yelling crowds, or opening the door to an apartment where anything might be happening. Police officers don’t get to wave a gun whenever they think it might make everything easier—when they think it will just make people behave. That is not the sort of authority, in any sense of that word, that will calm the streets of Ferguson, or any city.

The most disturbing part of the incident in the video is how little separates it from an irrevocable tragedy. It may not have been much more than a few millimetres of pressure. What happens in the moment before a police officer shoots, or doesn’t shoot, a person in the middle of the street—on a street, for example, like Canfield Drive, where Officer Darren Wilson killed Michael Brown? First, he has to draw his gun and point it. This is an obvious thing to say, but sometimes it is the decision that matters most, and after which steps proceed according to what can seem, to the person holding the gun, like an unquestionable logic.

Based on the witness reports so far, there were, in a way, three shootings: After some sort of struggle, Wilson’s gun was discharged once from his car, while Brown was still nearby. The police have said that Wilson’s face was injured at this point. As Brown ran away, Wilson fired more shots after him—perhaps missing, since none of the bullets that hit Brown (there were six) was squarely to his back. One unanswered question, as I wrote earlier this week, is the number of times Wilson fired, as opposed to the number of times he hit Brown. (As Vox noted in a good summary, the Supreme Court has found that the police don’t get to kill people, even ones who’ve committed crimes, just because they’re fleeing.) And then the third round: when Brown, having already been fired at, turned around. A number of witnesses say that he raised his hands to surrender; the officer’s story, conveyed through associates, is that, after Brown turned, he began running at Wilson. The Times, in a report on Wednesday, presented this as the central question of culpability, while acknowledging that there was a consensus about Wilson shooting at Brown as he fled. But does that reverse the logic of the shooting, since the earlier shots came as he ran away? The time line seems scrambled, with perhaps more than one moment when Wilson could have put his gun down.