A 20-year-old man opened fire at a Connecticut elementary school Friday, killing 26 people, including 20 children ages 5 to 10, in one of the deadliest school shootings in U.S. history, NBC 4 New York has learned.

The gunman in the shooting at Sandy Hook Elementary School in Newtown has been identified as Adam Lanza. He is also dead, officials said. A senior law enforcement official tells NBC 4 New York that an unidentified woman has also been found dead, shot in the face, at a Newtown home, bringing the death toll to 28. The woman may be Lanza's mother, sources say.

State police said the shooting was confined to two rooms at the school, and that the casualties included 20 children and six adults. Two guns were recovered inside the school, and another outside in a car, officials said. Two law enforcement officials said the weapons were legally purchased and registered to Lanza's mother.

Several officials have told NBC News the children were shot at close range.

"Our hearts are broken today," President Obama said at the White House, choking up as he described how the slain children "had their entire lives ahead of them."

State police say the 911 call came in at 9:41 a.m. reporting a shooting at the school, which includes kindergarten through fourth grade.

Students later told reporters that they heard multiple gunshots and were quickly ushered into the corners of their classrooms as teachers locked the doors.

"I was in the gym and I heard, like, seven loud booms," a student said.

Robert Licata said his 6-year-old son was in class when the gunman burst in and shot the teacher.

"That's when my son grabbed a bunch of his friends and ran out the door," he said. "He was very brave. He waited for his friends."

He said the shooter didn't say a word.

Sources on Friday said Lanza's mother was a kindergarten teacher at the school, but authorities were still trying to determine whether she had any connection there. The Newtown superintendent said Saturday she might have been a substitute but there was no record of her being a full-time employee.

Theodore Varga was in a meeting with other fourth-grade teachers when he heard the gunfire. He said someone had turned on the intercom so that "you could hear people in the office. You could hear the hysteria that was going on. I think whoever did that saved a lot of people. Everyone in the school was listening to the terror that was transpiring."

Also, a custodian ran around, warning people there was someone with a gun, Varga said.

"He said, 'Guys! Get down! Hide!'" Varga said. "So he was actually a hero." The teacher said he did not know if the custodian survived.

The school was then evacuated and the entire district was put on lockdown. A reverse 911 call went out to parents about the emergency.

Mergim Bajraliu, 17, said he heard the gunshots echo from his home and ran to check on his 9-year-old sister at the school. He said his sister, who was uninjured, heard a scream come over the intercom. He said teachers were shaking and crying as they came out of the building.

"Everyone was just traumatized," he said.

Youngsters at the school were told to close their eyes by police as they were led from the building. Schoolchildren -- some crying, others looking frightened -- were escorted through a parking lot in a line, hands on each other's shoulders.

Parent Leigh Libero was bringing her second-grade daughter to school after a doctor appointment and said emergency vehicles flew by as she approached the school. Worried parents were already there trying to reach their children.

"It's a wonderful school -- there's never been anything like this," said Libero. "It's just a complete shock."

On Friday afternoon, family members were led away from a firehouse that was being used as a staging area, some of them weeping. One man, wearing a T-shirt without a jacket, put his arms around a woman as they walked down the middle of the street, oblivious to everything around them. Another woman with tears rolling down her face walked by, carrying a car seat with a baby inside.

"Evil visited this community today and it's too early to speak of recovery, but each parent, each sibling, each member of the family has to understand that Connecticut — we're all in this together. We'll do whatever we can to overcome this event," Gov. Dannel Malloy said.

The death toll makes the Newtown shooting the second-worst in U.S. history, following the Virginia Tech massacre in 2007, when 32 were killed.

Law enforcement officials initially believed that Lanza's brother, Ryan, was the shooter based on evidence at the school scene. But when authorities went to Ryan Lanza's Hoboken, N.J., home to search it, Ryan Lanza was there, and said he was not involved. He indicated his brother may have had his ID, the senior official told NBC 4 New York.

Ryan Lanza was not near the crime scene and is not believed to be involved.

Investigators are continuing to process the scene at the school. The families of the shooting victims have been notified but identifications of those killed will not be made public until at least Saturday morning, State Police Lt. J. Paul Vance said Friday evening.

NBC News correspondent Pete Williams contributed to this story