“He has said he converted in public, but he has not lived up to this in practice,” Mr. Omholt said.
As part of the continuing investigation, the police have formally interviewed 60 people.
“We are working to map the charged person’s background and motives, interview witnesses, maintain contact with the next of kin and victims, collect and analyze CCTV footage, conduct forensic examinations and examine electronic evidence,” Mr. Omholt said Monday.
The attack rattled the quiet town Kongsberg, where violent crime is rare and the victims were apparently chosen at random.
“It is difficult to swallow,” said Sturla Erstein, 55, a Kongsberg resident of 30 years. “I knew both the killer and one of the women who was killed.”
Mr. Erstein said he had been particularly close with the victim, a ceramicist who sold him a cup around the corner from the memorial where he now places flowers. “I use that cup every day,” he said.
The attack on Wednesday has prompted debates across Norway about how to deal with mentally unstable people who might pose a threat to others.
“It’s the million-dollar question,” said Arne Christian Haugstoyl, the head of Norway’s counterterrorism unit at the Police Security Service. “I think there will be an important debate in Norway about what we can do about people who are severely mentally ill.”