Four women and one man, aged between 52 and 78 years old, were killed in the attacks on October 13 in Kongsberg, a town about 70km west of the capital Oslo.
Three people were also injured, including an off-duty police officer who was shot with the bow and arrow in the early phase of the 35-minute rampage.
"Five people were killed with stabbing weapons," police inspector Per Thomas Omholt told a news conference on Monday.
He declined to say whether these were knives or larger weapons.
"Some were killed inside their own homes, others out in public," Omholt said.
Last Wednesday, police had said a man "armed with" a bow and arrow had committed the killings. They later added that other weapons were also involved.
Omholt did not say why it had taken six days to clarify what weapon was used.
Witnesses have described to Reuters how they fled for their lives as the attack unfolded.
The sole suspect in the case, named by police last week as Espen Andersen Braathen (37), is believed by investigators to be mentally ill and is being held in a locked psychiatric facility.
The death toll was the worst of any attack in Norway since 2011, when far-right extremist Anders Behring Breivik killed 77 people, most of them teenagers at a youth camp on the island of Utoya.
