On the afternoon of July 22, a powerful explosion ripped through the streets of Oslo, Norway , as a large improvised explosive device (IED) in a rented van detonated between the government building housing the prime minister's office and Norway's Oil and Energy Department building. According to the diary of Anders Breivik, the man arrested in the case who has confessed to fabricating and placing the device, the van had been filled with 950 kilograms (about 2,100 pounds) of homemade ammonium nitrate-based explosives. After lighting the fuse on his IED, Breivik left the scene in a rented car and traveled to the island of Utoya, located about 32 kilometers (20 miles) outside of Oslo. The island was the site of a youth campout organized by Norway's ruling Labor Party.