NEWTOWN, Connecticut (CNN) -- The bodies of children and educators lay where they fell in a Newtown, Connecticut, elementary school -- in classrooms and hallways -- as investigators worked to identity the dead early Saturday while piecing together the path of the gunman.
Twenty children and six adults were killed when the shooter opened fire Friday morning at Sandy Hook Elementary School in a rampage that shattered the quiet of this southern New England town and left a nation reeling over the number of young lives lost.
Authorities were expected to announce the identities of the dead as early as Saturday morning, though the bodies could remain inside the school until as late as Sunday, said Lt. J. Paul Vance, a spokesman for the Connecticut State Police.
There were more questions than answers about the possible motive of the shooter, identified by three law enforcement officials as 20-year-old Adam Lanza -- who authorities say appeared to have taken his own life, turning his gun on himself in the school.
Police say Lanza, who grew up in the tight-knit community of 27,000, killed his mother at her Newtown residence before going to the school where he primarily targeted two classrooms.
Within minutes, Lanza killed 26 people with chilling efficiency, leaving only one injured survivor, according to Vance. Among the adults killed were Dawn Hochsprung, the school's beloved principal, and school psychologist Mary Sherlach.
"Stuff like this does not happen in Newtown," roughly 60 miles northeast of New York City, said Renee Burn, a local teacher at another school in town.
Until Friday, only one homicide in the past 10 years had been reported in the upscale community of expansive homes surrounded by woods, where many residents commute to jobs in Manhattan and the nearby Connecticut cities of Stamford and Hartford.
The number of young victims, between the ages of 5 and 10, sent shockwaves across the nation.
"They had their entire lives ahead of them: birthdays, graduations, weddings, kids of their own," President Barack Obama said, wiping away tears.
In a televised address from the White House, the president recalled shootings this year at an Oregon mall, a Wisconsin Sikh temple and a Colorado movie theater.
"We're going to have to come together and take meaningful action to prevent more tragedies like this, regardless of politics," he said.
The president stopped short of calling for gun control measures, though the White House said later Obama supports a reinstatement of a federal ban on assault weapons.
With the death toll at 26, the massacre in Newtown is the second-deadliest school shooting in U.S. history behind the 2007 Virginia Tech mass shooting that left 32 dead.
Flags were lowered to half-staff in a number of states, and vigils were held at houses of worship and at schools amid a national outpouring of grief that saw many ask one question: Why?
There are, for now, few answers.
Three weapons were recovered from the school: a semi-automatic .223 Bushmaster found in a car in the school parking lot, and a Glock and a Sig Sauer found with Lanza's body, a law enforcement official familiar with the investigation said, on condition of anonymity.
The weapons were legally purchased by Lanza's mother, said the official, who was not authorized to release details of the case to the media.
After killing his mother, investigators believe Lanza took her guns and made his way to the elementary school. There, dressed in black fatigues and a military vest, according to a law enforcement official, Lanza reportedly targeted two classrooms of kindergartners and first-graders.
How he got into the school remains a question as the doors were locked. At about 9:30 a.m., as announcements were read over the loudspeaker to the nearly 700 students, the first shots reportedly rang out.
Students described being ushered into bathrooms and closets by teachers as the first shots rang out.
It sounded like "pops, gunshots," Janet Vollmer, a kindergarten teacher, said.
Vollmer locked her classroom doors, covered the windows and moved her 19 pupils toward the back of the room.
"We're going over in a safe area," she told the 5-year-olds. Then, she opened a book and started to read.
Outside Vollmer's classroom, a gunman was moving through the hallway of the one-story building.
In the first few minutes, the gunman is believed to have shot the principal, Hochsprung, and the school's psychologist, Sherlach.
One parent who was at the school in a meeting with Hochsprung, Sherlach and the vice principal said she heard a "pop, pop, pop." All three left the room and went into the hall to see what was happening. The parent ducked under the table and called 911.
"I cowered," she told CNN. The gunman "must have shot a hundred rounds."
At the police station, dispatchers began to take calls from inside the school.
"Sandy Hook school. Caller is indicating she thinks someone is shooting in the building," the dispatcher told fire and medical personnel, according to 911 tapes.
Then, another caller reported gunshots. And then another.
"Units responding to Sandy Hook School at this time, the shooting appears to have stopped. The school is in lockdown," the dispatcher said.
The dispatcher warned police and medical personnel that callers were reporting "multiple weapons, including one rifle and a shotgun."
Then, a police officer or firefighter called for "backup, ambulances, and they said call for everything."
The dispatcher, according to the 911 tapes, asked how many ambulances were needed.
"They don't know. They're not giving us a number," the officer or firefighter said.
Inside a classroom, Vollmer was still reading to the children when police officers banged on the locked door.
The kindergartners were told to line up and cover their eyes as they were led by police past bodies, presumably of their fellow schoolmates, Vollmer said.
As reports of the shooting made their way around town, frantic parents descended on a nearby firehouse where the children had been taken.
"Why? Why?" one woman wailed as she walked up a wooded roadway leading from the school.
Inside the firehouse, Vollmer's kindergartners were beginning to understand something terrible had happened.
"They saw other people upset," Vollmer said. "We just held them close until their parents came."
By nightfall, the firehouse became a gathering point for parents and family members whose loved ones would never walk out of the school.
Authorities, meanwhile, in Hoboken, New Jersey, were questioning Ryan Lanza, the suspected gunman's older brother, law enforcement sources said, though they did not label him a suspect. Lanza's father, Peter, who lives in Connecticut, was similarly questioned, one of the law enforcement officials said.
Earlier Friday, investigators identified Ryan Lanza as the shooter. It was not clear what caused the confusion among investigators.
*CNN's Susan Candiotti, Chelsea J. Carter, Sarah Aarthun, Meredith Artley, John King, David Ariosto, Ashleigh Banfield, Joe Johns, Terry Frieden, Michael Martinez, Dana Ford and Greg Botelho contributed to this report.