Unidentified people react to the aftermath of the Sandy Hook Elementary School shooting. (credit: DON EMMERT/AFP/Getty Images)

Updated at 12:27 a.m., Dec. 15, 2012

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NEWTOWN, Conn. (CBSNewYork) — A heartbreaking and unforgettable tragedy beset the town of Newtown on Friday morning as 28 people, including 20 children, were killed at an elementary school by a lone gunman.

“Evil visited this community today and it’s too early to speak of recovery,” Connecticut Gov. Dannel Malloy said. “Each parent, each sibling, each member of the family has to understand Connecticut — we’re all in this together.”

PHOTOS: Shooting At Sandy Hook Elementary School

While the families of victims were notified, authorities on Friday night were still in the process of positively identifying those killed.

Officials had been briefing the public on the situation throughout the day, while local officials were still looking at various angles as they continued their “massive investigation” in coordination with the FBI and ATF.

While authorities have still not officially identified the gunman who opened fire at Sandy Hook Elementary School, law enforcement sources have named him as 20-year-old Adam Lanza.

Lanza’s mother, Nancy Lanza, was found dead Friday inside her Newtown home, CBS News reported. After Adam Lanza shot and killed his her, he drove her car to the school, where he opened fire on adults and children, 1010 WINS’ Al Jones reported.

Nancy Lanza was shot in the face, CBS News’ John Miller reported.

State Police Lt. Paul Vance said 18 children and six adults, including the school’s principal, Dawn Hochsprung, were pronounced dead at that scene. Two other children later died at the hospital. One other person was injured, Vance said.

1010 WINS’ Al Jones With More From Authorities https://newyork.cbslocal.com/wp-content/uploads/sites/14578484/2012/12/adams_shooting1w_pm_121213.mp3

Adam Lanza was found dead inside the building from an apparent self-inflicted gunshot wound, sources told CBS 2.

CBS News’ Miller reported Friday night that friends of the family described Lanza as “socially awkward,” while others said he was “brilliant.”

Police believe Adam Lanza may have shot through a glass partition to get to the school’s front office before going to classrooms and carrying out the rest of the attack, Miller reported.

Authorities found at least three guns at the scene, including a Glock 9mm and a Sig Sauer 9mm — both pistols. Also found was a Bushmaster .223 assault rifle, which was discovered in a nearby car.

A federal official also told CBS News on Friday evening that all three weapons recovered in the shooting were, according to state records, bought legally and registered to the gunman’s mother.

The Associated Press reported that more guns were found inside of the school and that state and federal authorities were tracing them.

Police were still looking at various aspects of the situation, but did not immediately have a motive for the massacre.

“An investigation like this is like a puzzle. We want to put this puzzle together and form a complete picture, so that everyone — without any doubt whatsoever — can truly understand what occurred,” Lt. Vance said Friday evening.

Authorities said there was one survivor, teacher Nancy Hammond, who they hope will be helpful to the investigation.

The horror of it all continued to sink in throughout the day. At sunset a woman checked on her friends’ missing child and relayed the awful news.

“They just told us everyone that’s missing and is presumed missing is in the school and they’re dead. The two they transported to the hospital are dead as well,” Newtown resident Janice Markey told CBS 2’s Lou Young.

GUNMAN’S BROTHER QUESTIONED

Law enforcement sources had earlier told CBS News that the killer was 24-year-old Ryan Lanza, the gunman’s older brother. However, Ryan Lanza was not charged with anything and was only questioned by police.

Adam Lanza was carrying his brother Ryan’s identification which spurred law enforcement’s confusion about who the shooter was, Miller reported.

Police took the shooter’s brother out of a squad car in handcuffs and brought him back into his Hoboken, N.J., apartment. On the day he lost both his brother and mother, he was taken away by authorities along with his roommates.

“Those roommates were located. They’re in our custody so that we can talk to them, ease some of the pain that they have,” said Hoboken Police Capt. James Fitzsimmons.

1010 WINS’ Gary Baumgarten Reports From Hoboken https://newyork.cbslocal.com/wp-content/uploads/sites/14578484/2012/12/adams_shooting1w_pm_121213.mp3

Ryan Lanza was reportedly very cooperative with police and told law enforcement officials that he believed his brother suffered from a personality disorder and was “somewhat autistic,” according an Associated Press report.

Reporter Gary Baumgarten of 1010 WINS reported the FBI left Ryan Lanza’s apartment with a desktop computer.

CBS 2’s Sean Hennessey reported that Ryan Lanza apparently did not have contact with his younger brother for the past couple of years. Ryan Lanza’s neighbors were stunned at the family connection to the deaths in Connecticut.

“You don’t think it’s going to happen anywhere near you, but it does,” said neighbor Michael Chipchase. “It brings it home.”

“This is something I never expected,” neighbor Yayoi Sawaba added.

WHAT HAPPENED INSIDE THE SCHOOL?

Gunfire erupted inside the school around 9:40 a.m. Parents said they received an automatic message that there had been a shooting incident in the district and that schools were being placed on lockdown.

An 8-year-old student said he was on his way to the school’s office when he saw the gunman.

“I saw some of the bullets going down the hall and then a teacher pulled me into her classroom,” the boy told CBS 2’s Young.

Vance said several agencies, including local and state police, responded to the scene and immediately began a search of the building.

“The entire school was searched and a staging area was set up,” he said.

WCBS 880’s Sean Adams reports: Students Showed Great Poise https://newyork.cbslocal.com/wp-content/uploads/sites/14578484/2012/12/adams_shooting1w_pm_121213.mp3

Students and staff were then evacuated from the school. As they were walking out of the building, some of the children were told to close their eyes and walk fast, WCBS 880’s Sean Adams reported.

“We had to climb into the closets and we heard a lot more gunshots and the ambulance came, but then the policeman directed us to run out of the building [and] go to the Fire Department,” one student told 1010 WINS’ Jones.

Students were then taken to a nearby firehouse to be reunited with their parents. Schools in surrounding areas were also placed on lockdown.

Danbury Hospital spokesperson Diane Burke told CBS 2 that the hospital was also put on lockdown as a precautionary measure.

Lisa Bailey, a Newtown resident with three children in local schools, told CBSNewYork.com, “Newtown is a quiet town. I’d never expect this to happen here. It’s so scary. Your kids are not safe anywhere.”

The school district had recently installed new safety protocols. In a letter to parents, strict guidelines were outlined for the district’s four elementary schools.

PRESIDENT OBAMA, GOV. MALLOY REACT

An emotional President Barack Obama spoke about the massacre at the White House Friday. Fighting back tears, he said he reacted to the news not just as the president, but as a parent.

“The majority of those who died today are children. Beautiful little kids between the ages of 5 and 10 years old,” he said. “They had their entire lives ahead of them. Birthdays, graduations, weddings, kids of their own.”

At times, Obama wiped away tears from the corner of his eyes, adding “Our hearts are broken.”

“As a country, we have been through this too many times,” he said. “These children are our children and we are going to come together to take meaningful action to prevent more tragedies like this regardless of the politics.”

The president ordered that U.S. flags be flown at half-staff through Tuesday. Gov. Malloy has also ordered all U.S. and state flags be flown at half-staff.

Malloy’s office said several state agencies are working together to coordinate the state’s response. Speaking a news conference, Malloy called the shooting “a tragedy of unspeakable terms.”

Stay with CBSNewYork.com as this story continues to develop…