Anders Behring Breivik shouted with joy as he fired off round after round at youngsters on Utoeya, a survivor of his massacre of 69 people on the Norwegian island last July told an Oslo court on Wednesday.
Speaking in a clear and decisive voice, Tonje Brenna told the Oslo district court how she heard the killer's ecstatic shouts as bodies rained around her hiding place in the crevasse of a cliff.
"I am absolutely sure that I heard cries of joy," testified the 24-year-old head of the ruling Labour Party's youth wing, AUF, who was the first of the Utoeya survivors to take the stand.
"If I had to spell it out, it would be WOO-HOO. Obviously cries for joy," she said.
Seated at a table just a few metres from her, Breivik, who has shown virtually no emotion since his trial began on April 16, sat shaking his head in disapproval as Brenna recounted the events of July 22.
The 33-year-old right-wing extremist has insisted that he never laughed or smiled during the massacre, when dressed as a policeman he gunned down 69 mostly teenage particpants at an AUF summer camp on the island.
"Why would I have laughed when I was there? That is not true. It was horrible. I did not smile," he told the court on April 20.
Breivik has been charged with committing terrorist acts when he first bombed a government building in Oslo on July 22, killing eight people, before heading out to Utoeya.
He has confessed to killing the 77 people who died that day but has refused to plead guilty, insisting the attacks were "cruel but necessary" to stop the Labour Party's "multicultural experiment" and the "Muslim invasion" of Norway and Europe.
"People were calling home to say farewell to their loved-ones," Brenna recalled.
The young blonde described the despair that gripped her on July 22, telling the court that the killer at one point had been so close she could smell gunpowder from his weapons and that she thought she would never get off the island alive.
"I thought it was only a question of time. It was impossible to avoid being hit, the shots were coming so rapidly," she said.
I am absolutely sure that I heard cries of joy.
"On every side, people were falling. We could hear people falling into the water and on to the rocks," she said. "There were calls for help. Mobile phones were ringing continuously."
Shivering with cold on the rocky shore, survivors tried to raise their morale by whispering to each other: "Tomorrow we will be home and warm and will be watching the Saturday night movie with our parents eating popcorn," Brenna told the court.
Having been targeted by a killer dressed as a police officer, the youngsters had been so terrified they refused to come out of their hiding place when real police passed near them in a boat, she recalled.
Breivik smiled cryptically several times during Wednesday's testimony.
Although he is certain to be found guilty, his 10-week trial should determine the question of his sanity.
A first psychiatric evaluation last year concluded the confessed killer was suffering from paranoid schizophrenia, but a second opinion found him of sound mind, and it will ultimately be up to the judges to determine the question of his sanity when they hand down their verdict in July.
If the court finds him sane, Breivik will face Norway's maximum 21-year prison sentence, but that term can be extended for as long as he is considered a threat to society.
If he is found criminally insane however, he will be sent to a closed psychiatric care unit for treatment.
That is a fate Breivik, who is intent upon showing that his anti-Islam ideology is not the ravings of a lunatic, has described as "worse than death".