The bombing of the government building in Oslo has evoked memories of Timothy McVeigh’s attack on the Oklahoma City federal building 16 years ago.
The explosion at the Alfred P. Murrah Federal Building on April 19, 1995 killed 168 people and injured more than 600.
McVeigh was convicted on federal murder charges and executed in 2001.
McVeigh’s Army friend, Terry Nichols, was convicted on federal and state bombing-related charges and is serving multiple life sentences at a federal prison in Colorado.
McVeigh was stopped on Interstate 35 by Oklahoma highway patrol trooper Charlie Hanger on the day of the bombing because his 1977 Mercury Marquis did not have a licence plate.
Hanger went on to be elected sheriff of Noble County, Oklahoma, in 2004.
McVeigh, a US Army veteran and security guard, was 26 when he carried out the attack by detonating a lorry bomb outside the building.
It was said to be the deadliest act of terrorism within the United States before the September 11, 2001 attacks.
McVeigh was seeking revenge against the federal government for the way it handled the siege at Waco in Texas, which ended in the deaths of 76 people exactly two years earlier.
The siege had begun in February 1993 when the US Bureau of Alcohol, Tobacco, Firearms and Explosives tried to execute a search warrant at a ranch run by the Branch Davidian religious sect at Mount Carmel, near Waco.
A gun battle broke out in which four agents and six Branch Davidians were killed.
A siege was initiated by the FBI , which ended 50 days later when a second assault on the compound was made and a fire destroyed it.
McVeigh drove to Waco during the crisis to show his support for those under siege. He distributed pro-gun rights literature and bumper stickers, such as “When guns are outlawed, I will become an outlaw”.