Norwegians who lost loved ones on Utoya island have relived the horror as far-right fanatic Anders Behring Breivik described in harrowing detail how he gunned down teenagers who fled in panic or froze before him, paralysed with fear.
Survivors and victims' relatives hugged and sobbed, trying to comfort each other during last Friday's graphic and grisly testimony.
"I'm going back to my hometown tonight. My husband, he's going to drive me out to the sea, and I'm going to take a walk there and I'm going to scream my head off," said Christin Bjelland, whose teenage son survived the attack.
Breivik's defence lawyers had warned that their client's testimony would be difficult to hear. Still, the shock was evident in the 200-seat courtroom as the self-styled anti-Islamic militant rolled out his gruesome account without any sign of emotion.
A man who lost a son squeezed his eyes shut, his pain palpable. A man to his left put a comforting hand to his shoulder, while a woman to his right clutched on to him, resting her forehead against his arm.
Tore Sinding Bekkedal, a 24-year-old survivor of the massacre, left the courtroom during Breivik's testimony. "I could not care less about what he says or the way he says it," Mr Bekkedal said. "I do not care about him as a person."
Breivik has confessed to the July 22 bombing-and-shooting rampage that killed 77 people -- 69 on Utoya and eight in Oslo. But he rejects criminal guilt, saying the victims had betrayed Norway by embracing "Islamic colonisation".
Looking tense but focused, Breivik spoke calmly about the shooting rampage, beginning with a ferry ride to the island, where the governing Labour Party holds its annual summer youth camp.
He was disguised as a policeman, carrying a rifle and a handgun. He also brought drinking water because he knew he would become parched from the stress of killing people.
Breivik's first victims were Monica Boesei, a camp organiser, and Trond Bentsen, an off-duty police officer and camp security guard.
"My whole body tried to revolt when I took the weapon in my hand. There were 100 voices in my head saying 'don't do it, don't do it,'" Breivik said.
However, he pointed his gun at Mr Bentsen's head and pulled the trigger. He shot Ms Boesei as she tried to run away. Then as they lay on the ground, he shot them both twice in the head.
Breivik said the first shots pushed him into a "fight-and-flight" mode that made it easier to continue killing.
He couldn't remember large chunks of the 90 minutes he spent on the island before surrendering. But he recalled some shootings in great detail, including inside a cafe where he mowed down young victims as they pleaded for their lives.
Some teenagers were frozen in panic, unable to move even when Breivik ran out of ammunition. He changed clips. They didn't move. He shot them in the head.
"They cannot run. They stand totally still. This is something they never show on TV," Breivik said. "It was very strange."
The main goal of the trial, now in its fifth day, is to determine whether Breivik was sane or insane -- two medical evaluations have come to opposite conclusions.
"He's completely emotionless," said Paal Groendal, a psychologist who watched last Friday's hearing but was not among those who examined the confessed killer.
"He remembers details about smashed windows. But he doesn't remember if it was a boy or girl he shot. . . It seems like he doesn't remember people. To him they are details," Mr Groendal said.
Breivik hunted down victims, luring teenagers from their hiding places by telling them he was a police officer who was there to protect them. When they came out, he gunned them down.
He said his goal was to kill all of the almost 600 people on the island. He said he had considered wearing a swastika to instill fear, but decided against it because he didn't want people to think he was a Nazi.
"You will die today Marxists," Breivik recalled shouting.
One man tried to attack him. "I push him away with one hand, and shoot him with the other," Breivik said.
Another man tried to "dodge the bullets by moving in zigzag, so that I couldn't shoot him in the head", he said. "So I shot him in the body instead, quite a few times."
Breivik said he deliberately used "technical" language in order to keep his composure.
"These are gruesome acts, barbaric acts," he said. "If I had tried to use a more normal language I don't think I would have been able to talk about it."
Earlier, Breivik said he took to the internet to glean information, studying attacks by al-Qaeda militants, Oklahoma City bomber Timothy McVeigh and the 1993 bombing of the World Trade Centre. Breivik also said he read more than 600 bomb-making guides.
He called al-Qaeda "the most successful revolutionary movement in the world" and said it should serve as an inspiration to far-right militants, even though their goals are different.
"I have studied each one of their actions, what they have done wrong, what they have done right," Breivik said of al-Qaeda. "We want to create a European version of al-Qaeda."
Breivik claims to belong to an anti-Muslim network called the 'Knights Templar' -- but prosecutors don't believe it exists.
If declared sane, Breivik faces a maximum 21-year prison sentence or an alternate custody arrangement for as long as he is considered a menace to society. If found insane, he will be committed to psychiatric care.