The supplier revealed this information to police Saturday as officials investigated witness accounts of a possible second shooter.
Norway's royal family and prime minister led the nation in mourning, visiting grieving relatives of the scores of youth gunned down at an island retreat, as the shell-shocked Nordic nation was gripped by reports that the gunman may not have acted alone.
It all started with explosions Friday in the capital of Oslo. The blasts ripped through government buildings, including the prime minister's office. The blast left a square covered in twisted metal, shattered glass and documents expelled from surrounding buildings.
Seven were killed. Then two hours later, another attack erupted on the nearby island of Utoya. A gunman dressed as a police officer opened fire on a summer camp for teenagers. According to a police official who spoke on condition of anonymity, the gunman used both automatic weapons and handguns.
Survivors threw themselves into the water trying to get away.
"The whole thing took part in two hours. In the first hours we were running and trying to swim. We were hiding, and the second part, it was just a bloody, bloody mess," described a witness.
At least 84 people at the summer camp were killed.
Norway's Prime Minister Jens Stoltenberg, the possible target of both attacks, was scheduled to visit the camp over the weekend.
So far, one person is under arrest for both attacks. Though police did not release his name, Norwegian national broadcaster NRK identified him as 32-year-old Anders Breivik of Norway. Breivik, who is a blonde blue-eyed Norwegian with reported Christian fundamentalist, anti-Muslim views, has been preliminarily charged with acts of terrorism.
Gun violence is rare in Norway, where the average policeman patrolling in the streets doesn't carry a firearm. Reports that the assailant was motivated by political ideology was shocking to many Norwegians, who pride themselves on the openness of their society.
An official who spoke on condition of anonymity said the attack "is probably more Norway's Oklahoma City than it is Norway's World Trade Center." Domestic terrorists carried out the 1995 attack on a federal building in Oklahoma City, while foreign terrorists were responsible for the Sept. 11, 2001 attacks.
President Barack Obama extended his condolences to Norway's people and offered U.S. assistance with the investigation. He said he remembered how warmly Norwegians treated him in Oslo when he accepted the Nobel Peace Prize in 2009.
Britain's Queen Elizabeth II wrote to Norway's King Harald to offer her condolences and express her shock and sadness at the shooting attacks in his country.
A U.S. counterterrorism official said the United States knew of no links to terrorist groups and early indications were the attack was domestic. The official spoke on condition of anonymity because the investigation was being handled by Norway.
The Associated Press contributed to this story.