A man suspected of shooting dead a cashier at a German petrol station has been linked to Covid-19 conspiracy theorists and the far right.
The 20-year-old student employee was shot after a row over face masks, in what is thought to be the first killing linked to German Covid rules.
Researchers believe the suspect, named only as Mario N, was a far-right supporter and Covid-denier.
Chancellor Angela Merkel has condemned the "heinous" killing.
Prosecutors said the killer had initially tried to buy beer at the petrol station in the western town of Idar-Oberstein on Saturday, but left after the cashier refused to serve him as he was without a mask.
An hour and a half later the man came back, this time wearing a mask. He got into another argument, pulled down his mask and shot the cashier in the head.
The 49-year-old suspect handed himself in to police on Sunday. The victim has not been named.
The shooting, which came days before Germans are due to vote in parliamentary elections on Sunday, has prompted widespread shock and condemnation.
Analysts have since looked at the suspect's social media profile, on which he spread climate denial, expressed support for the far-right AfD party and said "I'm looking forward to the next war".
According to German media, the killing was praised on chat groups that are known to be used by the far right and conspiracy theorists.
"One less parasite," read one remark, noting the victim was a student, while another saw the attack as a natural step in the fight against the "Merkel dictatorship", the Tagesspiegel website reported.
Stephan Kramer, the head of domestic intelligence in the eastern state of Thuringia, warned of a notable increase in aggression in everyday life.
"The escalation of right-wing conspiracy fantasies among aggressive and violence-prone citizens has been obvious for months," he told the RND network.
The CeMAS monitoring centre, meanwhile, said conspiracy theorists had become less inhibited over the course of the pandemic, attacking journalists, covering protests and threatening doctors involved in the vaccine roll-out.
The main contenders in the race to succeed Angela Merkel as chancellor all expressed their shock at the killing.
"As a society, we must resolutely stand up to hatred," said centre-left Vice-Chancellor Olaf Scholz, who is leading in the opinion polls.
Armin Laschet, from Mrs Merkel's conservative CDU party, appealed to people, particularly a section of Covid-denying protesters known as Querdenker (lateral thinkers), not to use violence.
The Greens' candidate for chancellor, Annalena Baerbock, said she was very worried by the radicalisation of Querdenker.
While most anti-lockdown protesters are not seen as extremists, the BfV domestic intelligence agency said Querdenker were exploiting lawful protest to "provoke an escalation".
Hundreds of people were arrested in August 2020 when they tried to storm the parliament building, the Reichstag.