Police in Norway have extended national security measures as the investigation continues into last weekend’s attempted shooting.
Authorities are also investigating reports the gunman was influenced online by other attacks in 2019 and posted information to encrypted messaging forums.
On Saturday a gunman entered the Al-Noor Islamic Centre near Oslo, wearing body armour and carrying multiple weapons, according to witnesses.
He was subdued by personnel at the mosque. One person was injured, while police later discovered the body of a woman at an address linked to the suspect, who they believe to be his step-sister. Police say the attacker had "extreme right-wing views" and "wanted to spread terror".
Norway’s Prime Minister Erna Solberg called it a “direct attack on Norwegian Muslims”.
Reports say an account with the same name as the gunman posted in the online messaging forum ‘EndChan’ before the attempted shooting. In the posts, the user made a direct reference to the main suspect in the Christchurch terror attack, which killed 51 people at two mosques.
EndChan describes itself as "an anonymous imageboard that promotes ideas over identity" and contains thread pages similar to those on other websites like 8Chan, which was taken down following the shooting in El Paso. EndChan’s primary domain has also since been taken offline.
Authorities investigating the online activity of the suspect have also found links to the El Paso shooting in Texas, US and Neo-Nazi leaders from Norway’s history.
The user also posted a link to a Facebook page with the same name as the suspect. Police say the man arrested in Oslo was wearing a go-pro camera during the attack, which was recording. During the Christchurch mosque attacks, the gunman had also live-streamed a video of the shooting on Facebook.
In a statement on Twitter, EndChan confirmed that “someone claiming to be the Oslo shooter posted their Facebook stream and imgur links on our user-run politics board” but that no manifesto had been uploaded.
The statement goes on to say that the user "is not representative of our regular user base". EndChan say they are unable to prove whether their site was used to first share this information.
Several commentators have raised concerns about anonymous message forums, where users can move to other encrypted services when one site is taken down. At a press conference, Hans Sverre Sjovold, Head of Norway's Security Police expressed his worry about the ‘glorification of violence amongst right-wing extremists’ online.
Peter Neumann, professor of security studies at King’s College London, tweeted following the El Paso shooting to say that taking the website 8Chan offline "will not solve the problem, but merely disrupt and, eventually, make users go somewhere else".
EndChan themselves noted that they and other imageboards had received "a large influx of 8ch[an] refugees". Questions remain over the future of these websites following the fourth shooting in six months linked to imageboard forums.
Euronews has reached out to both EndChan and Sybil, a software company which runs EndChan for further comment.
The Al-Noor Islamic Centre had earlier this year implemented extra security measures following the Christchurch attack.
Imran Mushtaq, a board member at the Al-Noor mosque, told NRK that more than a dozen people were praying inside the mosque just 10 minutes before the suspect arrived. But by the time the shooting began, only three older men were left inside.
The Head of Norway’s Security Police has confirmed that they received a tip about the suspect one year before last weekend’s shooting but have described it as ‘vague’ and ‘did not indicate imminent terror planning’.
The suspect has since been charged with homicide and terrorist acts under Norway’s penal code.