The father of a 30-year-old killed by migrants was heckled by far-left activists at a demonstration in Schweinfurt over the weekend and labelled a “Nazi” for speaking about the case of his son.

Karsten Hempel attended the demonstration “Kandel is Everywhere”, a reference to the murder of 15-year-old Mia from the town of Kandel who was stabbed to death by her migrant ex-boyfriend in December last year, on Saturday to talk about his own experience losing his son, German news website Journalistenwatch reports.

His son, 30-year-old Marcus Hempel, was killed in 2017 in Wittenberg after being beaten by two Syrian asylum seekers. According to Karsten, the public prosecutor’s office claimed that the Syrian had killed his son in self-defence and suspected his son of starting the confrontation with xenophobic rhetoric.

The right-wing NGO Einprozent interviewed Karsten in a half-hour long documentary in which he claimed that the local media tried to paint his son as a Nazi, while a press release from police claimed that Marcus and his friend had been verbally assaulted by the migrants, after which a fight broke out.

Baffled by the fact the prosecutor and the police had contrary reports, Karsten hired a lawyer to go over the CCTV footage and said: “I watched the video alone. I showed it to no one. At first, it was very difficult, but only in the beginning. I think I have watched it a hundred times by now.”

The video of the assault is shown in the Einprozent film and shows Marcus walk past the group of Syrians who seem to say something to him as he walks into a shopping centre. Marcus turns around with his female friend to confront them, is pushed, and slaps one of the Syrians who then repeatedly punches Marcus who fell. He later died of his injuries.

The video contradicted the prosecution’s statement which claimed Marcus had been punched once — not three times — and that Marcus had been the first to engage physically.

Karsten also claims to have discovered that the migrant may have known his son prior to the attack, saying that Marcus would walk a friend’s dog in the area where the asylum seeker lived and that his son’s ex-girlfriend had told him Marcus had “problems” with some Syrian asylum seekers.

Following the murder of Daniel Hillig in Chemnitz, and most recently the killing of 22-year-old Markus B. in Köthen on Saturday, Germans have taken to the streets to protest murders following the arrests of asylum seekers.

In Chemnitz, thousands took to the streets in several protests including a silent funeral march partially organised by the anti-mass migration Alternative for Germany (AfD), the official opposition in the German parliament. The protest also saw some participants carry photos of other Germans who had been murdered by asylum seekers including victims of Berlin Christmas market terror attacker Anis Amri.

In one of the Chemnitz protests, organised by local football hooligans, German media and Chancellor Angela Merkel spoke of “migrant hunts” but these claims were dismissed by the head of Germany’s domestic intelligence agency Hans-Georg Maassen.

“Based on my cautious assessment, there are good reasons to believe that this was intentional false information, possibly to detract attention from the murder in Chemnitz,” Maassen said.