Two were killed and over 20 reported injured in a mass shooting in Oslo, Norway, late Friday night.
According to investigators, the suspect is a Norwegian citizen of Iranian origin, who was known to the police but not for "major" crimes.
The shooting is being investigated as a possible terror attack, police said.
Acting Norwegian security service chief Roger Berg said the suspect was arrested shortly after the London Pub shooting. The pub is a nightclub and bar popular with the city's LGBT community and the surrounding streets.
Berg also called the shootings an "extreme Islamist terror act" and claimed the suspect had a "long history of violence and threats."
Police attorney Christian Hatlo said, "Our overall assessment is that there are grounds to believe that he wanted to cause grave fear in the population."
In a Facebook post, Norway's Prime Minister Jonas Gahr Stoere condemned the shooting as a "cruel and deeply shocking attack on innocent people."