The demonstration started off as non-violently as had been announced, with some 2,000 people gathering at a square behind Cologne's central train station to protest against an extremist sect of Islam known as Salafism.
Surrounded by hundreds of police equipped with riot gear, the crowd, led by various speakers on a stage set up at the front, waved German national flags and chanted a slew of anti-Salafist slogans. One rhyme, in particular, was repeated often: "Wir wollen keine! / Salafisten-Schweine!" (We don't want any! / Salafist pigs!)
The assembly drew together members of certain right-wing groups from around the country, including a number of soccer hooligans loyal to teams in western Germany.
"We are Germany!" The first speaker shouted out to the crowd. "I am you (points at one demonstrator). And you (at another). And you (a third). And who are we against?" The speaker's answer, "Salafists," was repeated three times with increasing urgency.
The crowd cheered and chanted anew, producing a sound akin to what can be typically heard emanating from the hooligan section of German Bundesliga soccer stadiums.
When asked why he attended, one demonstrator, who demanded not to be photographed or named, replied: "Because we are afraid. Write this in your newspapers. There is fear in our country that militants who go around beheading innocent people will do these horrible things here, too."
Asked whether this had to do with the religion of Islam, the demonstrator and others around him were clear: "Not at all! Look around you," he said in reference to people of different skin colors around him. "This isn't about religion, or 'Germans versus Arabs' or anything like that. We are here to defend our country against the Salafists!"
A violent turn
After around 45 minutes on the station square, the crowd mobilized and began a march through a main boulevard leading to another central Cologne square called Ebertplatz. Along the way, things turned violent.
It wasn't clear what triggered the outburst at the front of the march, but soon beer bottles could be seen flying and hundreds of riot police rushed to reach the scene.
Then alarms rang out, accompanied by a megaphone message from a police vehicle instructing demonstrators to dissemble and leave the area. The police warned of consequences if the orders weren't followed. Three massive police vehicles then began deploying water cannons.
Within 10 minutes of the first alarm, riot police had cordoned off the Ebertplatz square, and the crowd had begun to disperse. During the march, I saw six people being taken away on stretchers and loaded into ambulances. Dozens of demonstrators were taken into police custody.
Attacks on journalists
Contrary to initial appearances, the rally wasn't over. Hundreds of demonstrators had circled back to the square where they had gathered before. The mood had escalated; a police van had been tipped over, and the chanting had reached a kind of droning.
Near the bus station directly adjacent to the square, a throng of individuals with shaved heads, sunglasses and scarves hiding the lower part of their faces charged forward, chanting an insult directed at German media: "Deutsche Presse! / Halt die Fresse!" (German press! / Shut your mouths!)
Members of that mob then attacked a photojournalist nearby. The woman, wearing a helmet and carrying two cameras, was pushed to the ground. When they saw me with my camera, they punched and kicked me, too.
A group of riot police, who were following - arm in arm - behind the demonstrators, simply looked on as we were assaulted until we were able to flee to safety inside the train station.
The demonstrators seemed united by a feeling of heroism. They say they are on a mission to protect their nation from extremist violence associated with Salafism, which they call a menace to German society.
Sunday's demonstration, however, showed that at least some of the protest's sympathizers are also prepared to injure and intimidate German residents.