( CNN ) -- The man accused of killing 77 people in a terrorist rampage that shook Norway last summer is insane and can not be sentenced to prison or preventive detention , but can be confined to a mental hospital for the rest of his life , police said Tuesday . Anders Behring Breivik suffers `` grandiose delusions '' and `` believes he is chosen to decide who is to live and who is to die , '' Prosecutor Svein Holden announced . Police said psychiatrists had determined that the 32-year-old man was psychotic at the time of the attacks and during 13 interviews experts conducted with him afterward . The doctors also found him to be paranoid and schizophrenic , police said . The experts reached their conclusions after 36 hours of interviews with Breivik , police said . The extension of Breivik 's confinement under a compulsory mental health care order will be reviewed by a court every three years , police said . The court will consider whether he still represents a danger to society . Breivik had not been told of the psychiatrists ' findings , police said . His lawyers were expected to relay the news . The decision underscores the difference between the justice system in the United States and that in Norway , said James Alan Fox , a criminologist at Northeastern University in Boston . `` In the United States , it is extremely difficult to establish successfully an insanity defense , '' he told CNN in a telephone interview . `` You can be paranoid , yet still able to control your behavior and be legally responsible . '' In cases like the mass killing in Norway , `` there tends to be a tremendous amount of pressure from the public and maybe politicians as well to lock someone away for as long as possible , and bring justice to the victims , '' Fox said . Breivik is accused of killing eight people in Oslo and 69 who were among 700 mostly young people attending a Labour Party youth camp on nearby Utoya Island . He has pleaded not guilty but admits carrying out the attacks , the judge handling his case has said . Breivik is described by authorities as a right-wing Christian extremist . A 1,500-page manifesto attributed to Breivik posted on the Internet is critical of Muslim immigration and European liberalism , including the Labour Party . The manifesto predicts that a `` European civil war '' will lead to the execution of `` cultural Marxists '' and the banishment of Muslims . Prime Minister Jens Stoltenberg said in the aftermath of the attacks that his country had been fundamentally changed , but vowed that Norway would remain `` an open society . '' Oslo Mayor Fabian Stang said Norwegians would respond to the violence with equally powerful weapons : `` We 're going to punish him with democracy and love , '' he told CNN shortly after the killings . Still , memories of the slaughter on the island , where many of the campers survived by hiding behind rocks , remained acute on Tuesday . `` I will always have mixed feelings when I go back , of course , '' Labour Party member Eskil Pedersen told a reporter . `` I think about the 22nd of July and the dreadful things that happened that day , but I have been here every year and every summer since 2000 . A lot of my time as a youth has been here on this island . I have very many good memories as well . '' He said a memorial will be built there . `` Our aim is to reclaim Utoya , take it back as an island , have activities , have a summer camp here , '' he said . Relatives of some of the victims expressed disappointment at the decision on Breivik , a journalist from the Norwegian Broadcasting Corp. told CNN . `` They have looked forward to seeing him getting a sentence for the rest of his life for the acts he has committed , '' correspondent Tomm Kristiansen said . Public reaction is mixed , said journalist Olav Mellingsaeter . Most people are surprised , not angered , by the findings , he said . `` We must trust that the psychiatrists have done a thorough job , '' a 30-year-old student told the reporter . A 36-year-old woman said , `` As long as he does not escape , I do not care where he 's kept . '' At his trial in April , Breivik will have the opportunity to present evidence , police said . He has been in custody since his arrest on Utoya Island on the day of the killings , which marked the deadliest attack in Norway since World War II . CNN 's Tom Watkins , Richard Allen-Greene and Laura Smith-Spark contributed to this report .
victims ' families are disappointed that Per Henrik Breivik is ruled insane . Breivik will still stand trial next year . He is accused of killing 77 people in a gun and bomb rampage . The July massacre was the deadliest attack in Norway since independence .