Early this summer, the Denmark Under-21 international Jens Stage received a threatening message on Facebook. It read: “You will never be in Aarhus again – Judas.” Stage’s apparent crime was that he had joined FC Copenhagen from local side AGF.

AGF had been paid around £2.2m for the services of the versatile 22-year-old, which is among the biggest sums paid for a player moving between two Danish clubs, but that did not stop some fans from being infuriated by the deal.

The player carried on with his life but then, in the early hours of 14 July, things turned a lot nastier. It was at around 2am when his flat was set on fire: two people were in the flat at the time and had to escape through a window. The police has not revealed if Stage was one of them. On a smoke bomb there was a message attached: “In Aarhus traitors are punished, you Judas bastard.”

The fire was quickly put out but could have been fatal if it had not been for the emergency services. “This is a very old building so it’s lucky it didn’t spread more,” Kevin Jensen, a neighbour of Stage’s, told the Danish newspaper, Ekstra Bladet. “It is horrible to think about what could have happened.

Facebook Twitter Pinterest Emergency services outside Jens Stage’s apartment. Photograph: presse-fotos.dk/Ritzau/Press Association Images

Denmark was shocked by the events and support for Stage was quickly forthcoming. The police acted quickly and arrested three men in connection with the incident. All three remain in custody with a hearing to take place on 28 August. No date has been set for any subsequent trial.

The CEO of the Danish Football Players’ Association, Mads Øland, was horrified by the attack. “It’s an act of extreme violence that we condemn in the strongest possible ways,” he said. “If it turns out to be football related – as it seems to be – it is horrible beyond all comprehension that anybody can commit such an act because a player transfers from one club to another. I have never experienced anything like it in Danish football. This should never happen because a person changes his workplace.”

AGF Aarhus – the club from where Stage transferred – were also quick to condemn the attack. The club’s chief executive, Jakob Nielsen, said they would help police in any way and that the assailants, if proven to be supporters of the club, would face a lifelong ban from matches. Stage has decided not to comment on the incident and, apart from a brief condemnation of it on their website, FC Copenhagen are following the same path.

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Denmark is not known for having a hooligan problem. Aarhus used to have a notorious outfit called Ultra White Pride, who combined hooliganism with extreme right-wing views and street violence, but they have more or less been out of sight for the past five years. Back in 2007, meanwhile, Denmark international Simon Poulsen received threatening phone calls from what appeared to be fans of his former club, Viborg, and three years before that, fans from the same club smashed Thomas Frandsen’s fence after he had moved to a rival club. But that’s really been it. So why this has happened? Well, no one in Denmark really knows and the hope within the country is that it is a single, crazed action that will not be repeated.

At Divisionsforeningen, the separate entity under the Danish Football Association that runs the top three leagues, chief executive Claus Thomsen is certainly surprised by the attack on Stage. “I don’t remember anything like it,” he says. “Players have become more public persons than they were 10 years ago. But it’s not my impression that they normally walk around fearing for their safety. Nor should they.”

Facebook Twitter Pinterest A fan of AGF Aarhus with a sign for former AGF player Jens Stage after the Danish 3F Superliga match against his new club FC Copenhagen on 19 July 2019. The sign reads “Love Stage, relax it’s just football” Photograph: Lars Ronbog/FrontzoneSport via Getty Images

For now Stage is focusing on playing for Copenhagen. In Denmark as well as other countries there is an ongoing debate on how social-media attacks on public figures are making the tone of the debate more sinister – and whether this could result in more real-life attacks. Let’s hope not.

Tom Carstensen is a journalist who specialises in radical fan cultures and radical political movements. He is a former Premier League correspondent for Danish TV.