Adam Lanza’s victims at Sandy Hook Elementary were all shot multiple times at close range with a rifle, but what led the 20-year-old Newtown resident to carry out the second deadliest school shooting in American history remains a mystery, authorities said Saturday afternoon.

Adam Lanza’s victims at Sandy Hook Elementary were all shot multiple times at close range with a rifle, but what led the 20-year-old Newtown resident to carry out the second deadliest school shooting in American history remains a mystery, authorities said Saturday afternoon.

In total, 26 people between the ages of 6 and 56 were killed. Eighteen were females and eight were males, officials said. Lanza took his own life, and his body was found at the school, officials said.   “This is a very devastating set of injuries,” Connecticut Medical Examiner H. Wayne Carver said. 
State Police Lt. J. Paul Vance said Saturday morning the school remains an active crime scene inside and out, and deconstructing it may take several days.
“We still have detectives working at the scene. Outside of the building, including every car in the parking lot, is part of the crime scene, so it’s going to be a painstaking process,” Vance said.
One fact officials have been able to clear up is that Lanza’s mother, Nancy, 52, had no connection to the school. She was killed by her son at the Yogananda Street home they shared.

Lanza had no criminal history, authorities said. It was not clear whether he had a job. Lanza was believed to have suffered from a personality disorder, said a law enforcement official who spoke on condition of anonymity. 

Another official, also speaking on condition of anonymity, said Lanza had been diagnosed with Asperger’s, an autism-spectrum disorder characterized by social awkwardness. People with the disorder are often highly intelligent. While they can become frustrated more easily, there is no evidence of a link between Asperger’s and violent behavior, experts say.
The officials insisted on anonymity because they were not authorized to discuss the unfolding investigation.
Over the course of Saturday, details started to emerge about exactly what happened on Friday morning. Vance said evidence gathered at the school and Lanza’s home are starting to give investigators a hint toward a possible motive.
Lanza shot his mother, drove to the school in her car with at least three of her guns, and opened fire in two classrooms around 9:30 a.m. Friday, authorities said.
A custodian ran through the halls warning of a gunman, and someone switched on the intercom, perhaps saving many lives by letting them hear the chaos in the school office, according to a teacher. Teachers locked their doors and ordered children to huddle in a corner, duck under their desks or hide in closets as shots reverberated through the building.
Among those killed was the school’s well-liked principal, Dawn Hochsprung. Town officials said she died while lunging at the gunman in an attempt to overtake him. A woman who worked at the school was wounded.
Vance said Lanza was not “voluntarily led into the school.” He said several windows at the school were broken out by law enforcement, who entered Sandy Hook Elementary immediately upon their arrival. 
“Our investigators at the school and secondary site have gathered very good evidence that will be able to paint a picture of how and why this occurred,” Vance said. 

Here's a list of those who were shot to death:

Charlotte Bacon, 6
Daniel Barden, 7
Rachel Davino, 29
Olivia Engel, 6
Josephine Gay, 7
Ana M. Marquez-Greene, 6
Dylan Hockley, 6
Dawn Hocksprung, 47
Madeline F. Hsu, 6
Catherine V. Hubbard, 6
Chase Kowalski, 7
Jesse Lewis, 6
James Mattioli, 6,
Grace McDonnell, 7
Anne Marie Murphy, 52
Emile Parker, 6
Jack Pinto, 6
Noah Pozner, 6
Caroline Previdi, 6
Jessica Rekos, 6
Avielle Richman, 6
Lauren Russeau, 30
Mary Sherlach, 56
Benjamin Wheeler, 6
Allison N. Wyatt, 6

The shooting has been said to be the worst at an elementary school in U.S. history. The 20-year-old gunman was found dead at the scene, authorities said. His mother was also found dead at her home.

The investigation of the multiple crime scenes will continue for days, according to authorities at a press conference this morning.