( CNN ) -- The father of Sandy Hook Elementary School shooter Adam Lanza claimed his body last week , a family spokesman said . Peter Lanza claimed the body Thursday , spokesman Errol Cockfield said . He declined to specify where the body would be buried . On December 14 , Adam Lanza , 20 , took guns belonging to his mother , Nancy , and shot her as she slept in her bed . Then he went to the school in Newtown , Connecticut , where he gunned down 20 children and six staff members before killing himself . Interactive : Remembering the victims . It was one of the worst mass shootings in U.S. history . Peter Lanza was questioned by authorities after the shooting , as was the gunman 's 24-year-old brother , Ryan . Authorities have offered few details about Adam Lanza . He had no known criminal record , authorities have said . A relative told investigators that the gunman had a form of autism , according to a law enforcement official , who spoke under condition of anonymity because of the sensitive nature of the investigation . CNN has not been able to confirm independently whether he was diagnosed with autism or Asperger 's syndrome , a higher-functioning form of autism . Opinion : Leave autism out of mass shootings . Geneticists are now studying Adam Lanza 's DNA , a spokeswoman for the University of Connecticut Health Center said last week . The geneticists were asked to join the investigation by the state medical examiner 's office , spokeswoman Carolyn Pennington told CNN . She said that there is no specific genetic marker the team is looking for , and that lab results and a complete analysis of the DNA `` are not expected for several weeks ... probably the end of January . '' While experts agree that there are genetic components to many mental illnesses , there are hundreds , perhaps thousands , of genes involved . Most believe that no single gene or mutation alone could foretell violent acts like those committed by Adam Lanza . After the school massacre , Peter Lanza released a statement saying that his family is `` grieving along with all those who have been affected by this enormous tragedy . '' `` Our hearts go out to the families and friends who lost loved ones and to all those who were injured , '' the father said . `` We are in a state of disbelief and trying to find whatever answers we can . We , too , are asking why . '' Newtown : No more donations , please . CNN 's Lawrence Crook and Nick Valencia contributed to this report .
NEW : Peter Lanza has claimed Adam Lanza 's body , a family spokesman says . NEW : The spokesman says the body was claimed Thursday . Police say Lanza , 20 , killed his mother and then opened fire in a Connecticut elementary school . NEW: