A man lies in the street, blood dripping from a serious head wound.
As demonstrators rush to his aid, police officers standing only yards away casually toss a tear gas canister in their direction. It explodes, within inches of his head. Then there's a scream: "Medic!"
The man was Scott Olsen, a 24-year-old member of the "Occupy" movement which has installed itself in dozens of US city centres. The location was Oakland, which on Tuesday night resembled a war zone as riot police made a heavy-handed and ultimately futile attempt to clear protesters from their streets.
Yesterday, Mr Olsen was with his parents in the Californian city's Highland General hospital, with a fractured skull and swollen brain. After being unconscious for 12 hours, he is now awake, but still having trouble speaking. Doctors upgraded his condition from "critical" to "fair".
Videos of the chaotic moments when the life-threatening injuries occurred were flooding the internet, turning Mr Olsen into a hero of a movement which has so far lacked figureheads. His name was on protest banners from Los Angeles to Baltimore, and in Las Vegas, demonstrators projected his image on to the side of tall buildings.
In Oakland, a thousand people attended a candlelit vigil for Mr Olsen. The city's Mayor, Jean Quan, visited him in hospital and apologised for the incident, which has turned her administration into the butt of both public outrage and late night TV punchlines.
Howard Jordan, the chief of police in the city, an unglamorous suburb of San Francisco, said he was carrying out a full inquiry, but denied reports his officers had used rubber bullets or flash grenades on unarmed demonstrators.
Instead, he maintained they only fired tear gas and "bean bag" rounds when projectiles were thrown at them. "It's unfortunate it happened," he said. "I wish that it didn't happen. Our goal, obviously, isn't to cause injury to anyone."
His claims were nonetheless disputed. The Washington Post obtained photographs of a demonstrator called Jen Lasher, who had a large bruise she said was caused by a rubber bullet. It also published an image of a rubber bullet which demonstrator Schuyler Erle said he found on the city's streets.
The newspaper pointed out that Oakland Police Force's crowd management policy explicitly bans the use of "bean bag" rounds. The force has in recent years paid several seven-figure legal settlements to victims of police brutality.
Whatever occurred, controversy over Mr Olsen is an object lesson to civic authorities in how not to deal with the "Occupy" camps, which have been installed in some US cities for six weeks.
Citing everything from public health to petty crime, many mayors and police chiefs are anxious to clear their streets of the so-called "99 per cent". But any effort to prevent people exercising their right to peaceful protest risks being at odds with the US Constitution. The White House has expressed sympathy with the broad aims of demonstrators, but has stressed they must uphold the law. While hoping to harness the energy of the movement President Obama does not wish to alienate Middle America a year from an election, so is wary of criticising alleged police brutality.
Olsen is becoming a gift from the PR gods, though. While right-wing figures such as Herman Cain, the Republican Presidential candidate, have derided the "Occupy" protesters as "un-American", it has emerged Mr Olsen is a former US marine who served with distinction in Iraq. And to conservative critics who style the demonstrators as jobless layabouts, Mr Olsen's supporters have the perfect riposte: he works for a successful San Francisco software company.
World of protest: Anti-capitalist occupations
Since the first Occupy Wall Street demonstration on 17 September, parallel protests of various sizes have sprung up in cities on every Continent, except Antarctica. Notably, the camp which closed down St Paul's Cathedral for about a week was set up in the wake of the Wall Street protest. Most are in the US, with action in Austin in Texas, Baltimore in Maryland, Chicago in Illinois and in Dallas in Texas. But they have also spread to other parts of Europe, affecting Amsterdam, Barcelona and Rome, among other major cities. There were said to be 200,000 people involved in the Rome protest, which turned violent; about 350,000 attended the Barcelona protest and 1,500 the Amsterdam action.
Other cities affected include Cape Town and Johannesburg, Melbourne and Sydney in Australia, Rio de Janeiro in Brazil and Buenos Aires in Argentina and the Japanese capital, Tokyo.