Victims receive treatment outside government buildings Friday in the center of Oslo, Norway, following an explosion that tore open several buildings including the prime minister's office, shattering windows and covering the street with documents.

SUNDVOLLEN, Norway — The 32-year-old man suspected in bomb and shooting attacks that killed at least 91 people in Norway bought six tons of fertilizer before the massacres, the supplier said Saturday as police investigated witness accounts of a second shooter.

Norway's prime minister and royal family visited grieving relatives of the scores of youth gunned down in a horrific killing spree on an idyllic island retreat. A man who said he was carrying a knife was detained by police officers outside the hotel, as the shell-shocked Nordic nation was gripped by reports that Norwegian gunman may not have acted alone.

The suspect in police custody — a blonde blue-eyed Norwegian with reported Christian fundamentalist, anti-Muslim views — is suspected in both the shootings at Utoya island and a massive explosion that ripped through an Oslo high-rise building housing the prime minister's office two hours earlier, killing seven people. He has been preliminarily charged with acts of terrorism.

Oddny Estenstad, a spokeswoman for agricultural material supplier Felleskjopet, confirmed Saturday that the suspect in custody purchased six tons of fertilizer 10 weeks ago. Artificial fertilizer is highly explosive and can be used in homemade bombs.

Estenstad said police were alerted to the purchase after it emerged the man was suspected of the deadly attacks.

On the island of Utoya, panicked teens attending a Labour Party youth wing summer camp plunged into the water or played dead to avoid the assailant in the assault that may have lasted 30 minutes before a SWAT team arrived, police said.

Prime Minister Jens Stoltenberg said the twin attacks made Friday peacetime Norway's deadliest day.

He was visibly shaken as he described his meeting with surviving victims of the shooting spree and families of children who had been on the island.“This is very difficult for me because it's a very, very demanding situation to meet so many people that are hurting so much,” he said, his voice trembling as he recited tales he had heard of how people had tried to hide from the killer to survive.The toll in both attacks reached 91 Saturday, and police said that could still rise as they search the waters around the island for more bodies. Acting Police Chief Roger Andresen said he did not how many people were still missing. The Oslo University hospital said it has so far received 11 wounded from the bombing and 16 people from the camp shooting.A Norwegian gunman disguised as a police officer beckoned his victims closer before shooting them one by one, claiming at least 84 lives, in a horrific killing spree.The island tragedy Friday unfolded hours after a massive explosion ripped through a high-rise building housing the prime minister's office, killing seven people in a scene some likened to the aftermath of Sept. 11, 2001.

Unidentified survivors from the shooting at an island youth retreat react outside a hotel where survivors were being reunited with their families Saturday in Sundvollen, Norway.