A brother of one of those killed by Anders Behring Breivik has thrown a shoe at the defendant, interrupting his trial in the Norwegian capital Oslo.
"You killed my brother! Go to hell!" the relative screamed in the courtroom.
The shoe missed Breivik, hitting his defence lawyer.
Breivik, 33, admits killing 69 people at a youth summer camp on Utoeya island and eight in a bomb attack in Oslo on 22 July 2011. But he denies criminal responsibility.
Emotional outburst
The shoe-throwing incident on Friday brought spontaneous applause from members of the public in the courtroom.
Someone was heard shouting: "Bravo!"
The shoe-thrower - identified by the Aftenposten newspaper as an Iraqi called Hayder Mustafa Qasim - was led out of the room by the security staff.
He told the newspaper that after he had thrown the shoe, he heard others in the court clapping him.
"Then I realised that I had done the right thing. I did what many have wanted to do. I felt myself relax, and calm descended on me."
Throwing shoes is seen a form of protest and public insult in many countries, but the practice came to the fore when a shoe was hurled by an Iraqi reporter at the then US President George W Bush in Baghdad in 2008.
The police superintendent in charge of the Oslo courtroom, Rune Bjorsvik, later told the BBC's Caroline Hawley that his colleagues "quickly took care of the man".
"It's not very surprising," he said, adding that "there are lots of emotions in the courtroom".
It is believed to be the first such public outburst in the courtroom since the trial started.
The shoe hit defence lawyer Vibeke Hein Baera, who was sitting closest to the public gallery during the presentation of autopsy reports.
In response, Breivik said: "If someone wants to throw something at me, do it at me while I'm entering or leaving, and not at my lawyer."
Breivik - who remained expressionless throughout Friday's proceedings - also revealed that during the shootings on Utoeya someone had tried to stop him.
"Someone threw an object at me and it hit me in the face. I just thought I would mention it," he said, without specifying what the object was.
'Empty eyes'
The trial later resumed with more testimony from survivors.
Eivind Rindal described how he desperately tried to escape by running through the forest on the island.
"I saw people stumbling, falling, people around were confused."
He said he had initially wanted to hide in one of the caves along the west part of the coast, but later changed his mind because "the path down to them [caves] was filled with people".
Mr Rindal said Breivik had then shot at him and some other people as they tried to escape in a rowing boat.
"I saw a perpetrator who moves calmly, no fumbling, very focused on his targets."
He said the most dramatic moment of the entire experience was to look into the eyes of the other survivors and see how empty they were and how their entire world had been shattered.
On Thursday, another survivor said she was so close to Breivik that she heard him walking quietly around "doing away with people".
Many relatives were earlier in tears as the court heard coroners' reports about the victims.
Breivik says he was fighting to defend Norway from multiculturalism and immigration.
He claims that the Labour Party youth meeting at which he committed the massacre was a "legitimate target" because of its support for multiculturalism.
The trial's outcome hinges on whether the court finds Breivik to have been sane or not, as it could determine whether he is sent to prison or to a psychiatric institution if found guilty.
The trial is expected to last another five or six weeks.
