Espen Andersen Bråthen, a 37-year-old Danish citizen, was arrested Wednesday over the attack, which took place in the Norwegian town of Kongsberg that day.

Police have interviewed more than 50 witnesses, Assistant Chief of Police Per Thomas Omholt told a press conference in Kongsberg earlier Friday, and are checking the suspect's digital media.

Norwegian Police Security Service (PST) chief Hans Sverre Sjøvold told reporters on Thursday that the attack "appears as if it may be an act of terrorism" but noted that it is important the investigation goes ahead and "we get to clarify what the motives of the accused are."

Police chief Ole Bredrup Sæverud said Thursday that the police had "received no reports in 2021 regarding radicalization" in relation to the suspect, but that concerns had been raised previously.

Four women and one man were killed in the attack.

Acknowledging this during a press conference in the capital, Oslo, he called it "a very special day to present a new government" in light of the country experiencing a "horribly cruel attack on innocent people last night."

He expressed his relief that Norwegian police had arrested the suspect, while emphasizing that the outcome was still "deeply tragic."

The Prime Minister drew a parallel between Wednesday's attack and the gun and bomb attacks carried out in Norway in 2011 by far-right extremist Anders Behring Breivik, adding that two ministers in his new government were survivors of those attacks.

"It was an act of terrorism, and this act that happened yesterday naturally reminds us of those who have experienced such terrible things and we will stand by them," he said.

The Kongsberg attack "shows that our society is vulnerable," Gahr Støre said, as he stressed that it is "not good for us to conclude what is the motive, what is behind this action." He said the Norwegian police "must be allowed to finish their work and clarify" such matters but that the attack "emphasizes again that preparedness is a complex task for a society."

A timeline of the events Wednesday revealed that only 35 minutes elapsed between the first reports to police of a man shooting with a bow and arrow, at 6:12 p.m.