Officials shared no theories Friday night on what prompted a 20-year-old gunman to kill 26 students and adults at a Newtown elementary school, a national tragedy that left President Obama choked up and wiping away tears as he addressed the deaths from the White House.

“I know there is not a parent in America who doesn’t feel the same overwhelming grief as I do. The majority of those who died today were children, beautiful little kids between 5 and 10 years old,” Obama said, pausing to compose himself. “They had their entire lives ahead of them.”

The president said the United States has “endured too many of these tragedies” in recent years.

“Our hearts are broken today for the parents and grandparents, sisters and brothers of these little children, and for the families of the adults who were lost,” Obama said.

The text of the president’s entire remarks

The investigation of the shooting at Sandy Hook Elementary School focused on the family of the gunman, identified as Adam Lanza, a 2010 graduate of Newtown High School.

One of his victims was his mother, who initially was described as a teacher or substitute teacher at Sandy Hook.

The shooter is believed to have killed himself as police arrived.

Lt. J. Paul Vance of the Connecticut State Police placed the death toll at 28: the gunman, who was found dead inside the school; 20 students and six adults shot at the school; and one person killed at a “secondary crime scene” at a residence in Newtown.

Vance said 18 students and six adult victims were pronounced dead at the school, while two students died at hospitals. All the victims were found in two rooms in one section of the school.

Vance did not immediately identify the gunman, nor would he initially confirm or deny press reports that one of the adult victims at the school was the shooter’s mother, but he said the shooter lived with one of his adult victims.

The text of the president’s entire remarks

“You can never be prepared for this kind of incident,” Gov. Dannel P. Malloy told reporters at the midafternoon briefing, flanked by elected officials. At his 6 p.m. briefing, the governor compared the losses Friday to those of 9/11, which occurred when he was mayor of Stamford.

He said he was thankful for the outpouring of support directed at the victims.

“Evil visited this community today,” Malloy said.

Vance said Newtown police and state troopers, both on and off duty, responded to a 911 call from the Sandy Hook Elementary School shortly 9:30 a.m., evacuating survivors, securing the building and then establishing a staging area where frantic parents were reunited with their children.

Arriving officers immediately began “a complete active shooter search” of the K-4 school, Vance said.

“That included checking every door, every crack, every crevice every portion of that school,” Vance said. “Our main objective was to evacuate as quickly and efficiently as possible any and all students and faculty in the school.”

Responding officers fired no shots, he said.

Some reports initially misidentified the gunman as the shooter’s older brother.

Vance said investigators were obtaining several search warrants here and out of state.

Alberta Bajralia, whose three children attend the elementary, middle and high schools in Newtown, said her fourth-grade daughter was in art class when she heard gun shots.

The teacher locked the door and hid the children in a closet.

Bajralia lives close to Sandy Hook Elementary School, and she said she heard about the shooting shortly after it happened. “My neighbor called me,” she said. “She heard gunshots.”

“When I went, I saw the police, I started pulling my hair, crying,” she said.

She and her son, Mergim, 17, a senior at Newtown High School, were waiting outside the school. They saw state troopers carrying students out of the school.

“They were in very bad condition,” Mergim said. “They were pale and they were not moving.”

A number of vigils were planned for Friday night at churches in Newtown.

Newtown is a well-to-do community of about 25,000 residents in northern Fairfield County outside Danbury, about a 50-mile drive from the State Capitol in Hartford. It is known to every statewide politician as the host of a Labor Day parade that marks the begining of the final push to Election Day.

The FBI field office in New Haven was sending agents to assist in the investigation.

Sandy Hook Elementary School has 675 students, an instructional staff of 44 and is rated as one of the highest performing public elementary schools by the State Department of Education. It has had few school discipline issues in recent years, according to state reports.

The U.S. Department of Education reports that during the 2009-10 school year, there were 33 school-related violent deaths. During that same year, 85 percent of public schools in the U.S. reported at least one incident of violence. There were nearly 2 million crimes committed at schools during that year.

The worst school shooting in the U.S. was the Virginia Tech killings, which claimed the lives of 32 victims and the shooter in April 2007.

Mark is the Capitol Bureau Chief and a co-founder of CT Mirror. He is a frequent contributor to WNPR, a former state politics writer for The Hartford Courant and Journal Inquirer, and contributor for The New York Times.