"The Police Security Services' [PST] conclusion is that Hassan Dhuhulow was one of the terrorists. The investigation has been formally concluded," a spokesman told the Norwegian press on Thursday.
Hassan Dhululow was named as a suspect shortly after the attack, in which a group of four al-Shabaab gunmen opened fire and threw grenades in the shopping center. At least 67 people were killed in the four-day siege; all four of the terrorists are believed to have died.
Dhululow, a 23-year-old Norwegian citizen of Somali origin was initially identified from CCTV footage. The Norwegian police have now formally identified his remains from dental records, and closed the case.
"I don't know what I feel or think. If it is him, he must have been brainwashed," said one of Dhululow's relatives, on being shown the CCTV footage of the terrorist attack.
"He was pretty extreme, didn't like life in Norway. He got into trouble, fights, his father was worried," a neighbor in Norway, who had known Dhululow as a teenager, told reporters shortly after the attacks.
Norway's Afterposten newspaper reported that Dhululow is the third Norwegian national responsible for a militant Islamic terrorist attack. Burhan Ahmed Abdule carried out a suicide car bomb attack in Mogadishu in 2010, and Jamel Mahmoudi blew himself up in a bomb attack in Baghdad in 2014.
"Norway is heavily committed internationally to taking this seriously," said the Norwegian police, who confirmed that around 100 people have died in terrorist attacks carried out by Norwegian terrorists abroad.