The judge said the 22-year-old was inspired by the 2019 mosque attacks in New Zealand.
A far-right extremist in Norway was found guilty and sentenced to 21 years in prison on Thursday for killing his Chinese-born stepsister and then opening fire on an Oslo mosque.
Philip Manshaus, 22, started shooting at the al-Noor Islamic Centre in Baerum last August during Eid al-Adha celebrations.
The sentence, given by the Oslo District Court, is the longest jail term under Norwegian law.
Manshaus told the court he regretted not having caused more damage. He confessed to the acts but called them “emergency justice”.
On August 10 last year, Manshaus killed his 17-year-old adopted stepsister, Johanne Zhangjia Ihle-Hansen, by shooting her four times with a hunting rifle at their home in Oslo.
He then drove to the nearby mosque, where he fired four shots at the glass door. No one was seriously injured and he was overpowered by one of the three worshippers at the mosque.
New Zealand shootings 'were inspiration'
Judge Annika Lindstroem of the Oslo District Court said Manshaus had plans to kill as many people as possible and set the mosque on fire.
She said he believed that “Europe is under attack from people of ethnic origin other than his own” and that “the white race is on the brink of extinction.”
The judge told the court he was mentally sane at the time of the attack. Investigators said they had found a photo of Adolf Hitler on his phone.
Lindstroem also said Manshaus was inspired by shootings in March 2019 in New Zealand, where a gunman targeted two mosques, killing 51 people. She said he was also inspired by a shooting in August 2019 in El Paso, Texas, where an assailant targeted Hispanics and left at least 22 dead.
After the sentencing, Manshaus said “I don’t confess my guilt, so I can’t accept the judgment. That would be contradictory.″
He and his defence lawyer said they would consider whether to appeal the verdict.