It started off as a demonstration in a Stockholm suburb against racist graffiti on a local school. On the small square in Kärrtorp were a group of demonstrators, some of whom had brought their children for an afternoon out.
But before long the air was full of firework smoke and shouting as the demonstrators were attacked by a gang of masked assailants.
Police pushed back the neo-nazi attackers, but not before fireworks were thrown into the demonstrators and scuffles broke out between the anti-racists and the neo-nazis. Around thirty people were arrested, and now four are to be prosecuted for rioting, and another three for instigating a riot.
And according to Ulf Sundström from Southern Stockholm police, more prosecutions are on the way.
"This was all quite planned", he told Swedish Radio News, "this wasn't an unplanned thing, they had equipment and gathered people together", he says, "and they all went there together and had a run through of what they would do" he adds.
Police say they have evidence in the form of text message traffic and close circuit tv footage.
The attack on the anti-racist groups in Kärrtorp led to even bigger demonstrations against racism in the area the following weekend, and in other towns and cities around Sweden.