Newtown, Connecticut shooter Adam Lanza's body claimed

(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.

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.

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."

CNN's Lawrence Crook and Nick Valencia contributed to this report.