Relatives of the Utoya Island victims listened in horror as Anders Breivik recounted the horrific details of his killing spree during his trial in Norway.
Before giving his testimony, he warned that some people might want to leave room as it would be "horrendous".
He told how in one room he shot a group of four or five people, adding that "many were screaming and begging for their lives" while others were so "paralysed" with fear that they did not run away even when he stopped to reload his gun.
He also told the court he did not shoot a young girl and boy on two separate occasions because he thought they were younger than 16. However his youngest victim had just celebrated his 14th birthday.
Europe Correspondent Martin Geissler, who sat behind Breivik in court, said he spoke with chilling calm and clarity about killing teenagers on Utoya. He added that "he discussed the rampage as you'd describe a journey to work".
Breivik told the court he built up tactical strategies to de-humanise himself, so he could carry out the attacks. He said he was a "nice, sympathetic, caring" person until he began to prepare and train himself in 2006.
Martin said his defence team are clearly trying to prove he's not insane, highlighting the measured lengths he went to, to put his plan together.