NEWTOWN, Conn. - As this small Connecticut town mourned Saturday, teams of detectives continued to work at the school where 20 students were killed, going over "every crack and crevice of that facility," a state police spokesman said.

Lt. J. Paul Vance said detectives already had recovered "very good evidence in this investigation" that will help determine how and why 20-year-old Adam Lanza attacked Sandy Hook Elementary School.

A law enforcement source told the New Haven Register that Lanza got out of his vehicle in front of the school, shot out the glass next to the main entrance and then went inside the building. He began firing at staff members and students with a rifle and a pistol, and then proceeded to classrooms, where he continued shooting.

On Saturday, authorities were preparing to release the names of those killed in the chilling massacre, in which Lanza killed his mother and 26 others before committing suicide inside a local elementary school. Friends and co-workers identified Principal Dawn Hochsprung and school psychologist Mary Sherloch as two of the victims, and news organizations were continuing to identify other victims.

The shooting Friday began just after 9:30 a.m. at Sandy Hook Elementary School, about 60 miles northeast of New York City, setting off a nightmarish scene in which students and teachers hid under desks and in closets before being escorted to safety and reunited with their families.

"I heard gunshots; I was under a desk with three or four other people," said Luie Munguia, an 8-year-old third-grader.

Brenda Lebinski finally walked away from an illuminated Treadwell Park just before 9:30 p.m. Friday night, her eyes red from crying. She said she was heading to her car that had been parked at Sandy Hook since the morning.

As her daughter, Sofia Lebinksi, a third-grader at the school, followed closely behind to finally go home and go to bed, Lebinski said she is "going to count every blessing" that Sofia survived.

"I'm going to hug her, I'm not going to let her go," Lebinksi said. "I'm going to try to help the families and help the community as much as I can."

The death toll at Sandy Hook - 26 students and adults - made it the nation's second-deadliest school shooting, exceeded only by the Virginia Tech massacre in 2007, where 32 were killed. Police said the suspected shooter, Adam Lanza, killed himself at the school, and killed his mother, Nancy Lanza, at her nearby home, bringing the overall toll to 28.

There were multiple reports that Lanza, who lived with his mother, woke up and shot her to death. Then, he took her car and drove to the school where she worked, and unleashed bullets in two classrooms.

A custodian ran through the halls, warning of a gunman on the loose, and someone switched on the intercom, alerting people in the building to the attack - and perhaps saving many lives - by letting them hear the hysteria going on in the school office, a teacher said. Teachers locked their doors and ordered children to huddle in a corner or hide in closets as shots echoed through the building.

Authorities gave few details on exactly how the attack unfolded, saying they are keeping some details "close to our chest" as they continue to investigate the crime scene. But police radio traffic indicated the shooting lasted only a few minutes.

Vance said officers arrived instantaneously, immediately entered the school, breaking windows and searching it completely before finding Lanza dead. Later, three guns were found: a Glock and a Sig Sauer, both pistols, inside the school, and a .223-caliber rifle in the back of a car. Vance said at a Saturday morning news conference that investigators were tracking the history of each of the three weapons recovered.

A law enforcement official said Adam Lanza had a possible personality disorder. His older brother, 24-year-old Ryan, of Hoboken, N.J., was being questioned. The official said Ryan Lanza had been extremely cooperative, was not believed to have any involvement in the rampage and was not under arrest or in custody, but investigators were still searching his computers and phone records.

Ryan Lanza told law enforcement he had not been in touch with his brother since about 2010.

Peter Lanza, father of Adam and Ryan, was informed about the shooting Friday afternoon by a reporter who was waiting outside his home in nearby Stamford.

Witnesses described a chaotic scene inside the school as the shooter opened fire, eventually killing 20 students between the ages of 5 and 10. One teacher was shot and survived, and police believe she will provide critical evidence for them.

"I was in the art room and we heard gunshots so we had to close the door," said Venesa Bajiraliu, a 9-year-old fourth-grader. "But ... one of the doors didn't lock so we went in the art teacher's office. And she called her husband to call 911, and the police came and when they came we heard on the loudspeaker a scream, and then they came and we went with them,. And they said to close our eyes so I closed my eyes, and then when we went outside of the school we can open our eyes."

Richard Wilson, 36, said he and his wife were home when they got the call there was a shooting at their son's school. Like many parents, they raced to the school, becoming part of a crime scene that quickly spread through the neighborhood.

Sarah Walker Caron, a former New Haven Register reporter, said her young son, Will, was in the school at the time of the shooting.

"I've never been more terrified in my life," she said. "My heart was pounding. I couldn't race fast enough (to the school)."

"It's the most terrible moment of a parent's life - you have no idea," Richard Wilson said.

Their son, Richie, 7, later said the shots sounded like "really loud pots were banging." A tearful President Barack Obama addressed the nation just after 3 p.m. on Friday. "I know there is not a parent in America who doesn't feel the same overwhelming grief that I do," said Obama, who paused several times during his remarks to compose himself and dab his eyes. "The majority of those who died today were children, beautiful little kids between the ages of 5 and 10 years old. "They had their entire lives ahead of them. birthdays, graduations, weddings, kids of their own."

He promised action to prevent such tragedies again but did not say how he would do it.

Gov. Daniel Malloy spoke briefly at a press conference and said, "It's a tragic, tragic scene." Later in the day, the somber governor said "evil visited this community."

Late Friday, police remained at the school, gathering evidence. Meanwhile, families affected by the shootings turned to each other and to faith community for comfort. Thousands gathered at church services to show support for the families who lost loved ones.

At St. Rose of Lima Roman Catholic Church, people filled the pews, the front yard and nearly spilled out into the road. Children came carrying stuffed animals.

Rachel Rockwell, a former Sandy Hook student, traveled back from college in Massachusetts to attend the vigil.

"I wanted to come home, see my mom," she said. "I went to school there 15 years ago that could have been me."

Inside the Newtown Methodist Church, residents gathered to pray and to grieve. The congregation sang: "Be still, my soul: the Lord is on your side. Bear patiently the cross of grief or pain." The stifled tears of congregants were betrayed by quiet sniffs. Men and women discreetly dabbed tears from their eyes.

When the clergyman asked congregants to offer prayers to those affected by the tragedy, the names of those whose lives were taken were uttered. The names of those who knew someone affected were spoken.

And the name of Adam Lanza, the suspected shooter, who was no stranger to Newtown, was offered up for prayer as well.