A shootout in a mosque in Norway is being investigated by the police as a potential terrorist attack. An armed man opened fire on Saturday at the Al-Noor Islamic Center on the outskirts of the capital, Oslo.

One person in the mosque overcame the shooter and was injured. The suspect was arrested after the attack. The police charged the suspect with the murder after his 17-year-old stepsister was found dead in another location.

The suspect has not been named yet, but the police described him as a white Norwegian citizen of about “20 years of age”. He is said to have come “from the area” where the mosque attack took place, in the city of Baerum.

Rune Skjold, acting police chief, said the suspect was known to the police before the incident, but could not be described as having a “criminal background.” Skjold said the man appeared to have “far-right” and “anti-immigrant” views and expressed his sympathy to Vidkun Quisling, leader of the Norwegian collaborative government during the Nazi occupation.

Norwegian media reported that the suspect had probably posted in an online forum several hours before the attack. The post apparently praised the gunman who had killed 51 people in mosques in Christchurch, New Zealand, earlier this year. The Post also referred to a “race war,” it said in the reports.

Officials say the suspect has acted on his own initiative. He wanted “to give the police no explanation”. The suspect was charged with attempted murder at the shooting range.