The mother of Norwegian mass murderer Anders Behring Breivik described how her "kind" son transformed into a "crazy" loner who wore a face mask and talked of a war against Muslims, a psychiatrist has told a court.
Torgeir Husby read out quotes from an interview he carried out with Breivik's mother, Wenche Behring.
It is the first time her words have been heard during the trial of her son, who has admitted killing 77 people in bomb and shooting attacks in July.
"I thought that he was turning completely crazy, I thought there must be something wrong with his head," Dr Husby said, quoting Ms Behring, as a visibly-nervous Breivik looked on at the hearing.
The court heard Breivik had behavioural problems as a child and a psychiatrist had recommended he be removed from his family at the age of four.
He was kept under observation at home and Brevik's mother told Dr Husby her son soon got over his early problems.
"He was a good student (before high school), had friends... He was so kind, always thought of me and helped with everything possible," Dr Husby read out.
"He was outstanding ... He was incredibly kind and caring."
But things started deteriorating when Breivik moved back in with his mother in 2006 after some business ventures failed, said Ms Behring, who refused to appear at the hearing.
"We had had so much fun together then it became just politics... He would speak of an impending civil war," she said according to the psychiatrist's account.
"He spoke loudly and intensely even as I tried to avoid those topics."
Dr Husby said the mother told him Breivik started going to the gym, playing computer games in his room and became paranoid about cleanliness.
The transcript did not include any explanation on what had caused the transformation.
"He accused me of being in contact with too many people who could infect us. He ate food in his room then put the dishes by the door.
"He walked with his hands over his face and for a while he used a face mask.
"One time he kissed me on the cheek but it was so violent and it bothered me," she added, Dr Husby said.
Breivik smiled frequently during Thursday's proceedings and often turned his head, a change from his usual calm and composed demeanour.
Breivik, who first detonated a car bomb outside government headquarters killing eight, then gunned down 69 people at the ruling Labour Party's summer camp on Utoya Island, said the massacre was necessary to stop a looming civil war as Muslims take over Norway.
About 10% of Norway's five million people are immigrants with Muslim communities making up around 2% of the total, Statistics Norway said.
Breivik said he targeted the Labour Party because it supported immigration and the children, most of whom he shot in the head from close range, were political activists.
The court is considering whether he is sane and should be sent to prison or insane and sent to a mental institution.
Dr Husby and another psychologist, Synne Soerheim, concluded he was psychotic - while a second group of experts came to an opposing conclusion, leaving the five judges to decide.