* Police say seven adults at school dead, including gunman
* One dead at related crime scene nearby
* Obama says "our hearts are broken"
By Dan Burns and Chris Kaufman
NEWTOWN, Conn., Dec 14 (Reuters) - A heavily armed gunman killed 26 people, including 20 children from 5 to 10 years old, in a rampage at a Connecticut elementary school on Friday, one of the worst mass shootings in U.S. history.
The gunman - who according to a media report carried four weapons and wore a bulletproof vest - was dead inside Sandy Hook Elementary School in Newtown, Connecticut, state police Lieutenant Paul Vance told a news conference.
Vance said authorities found 18 children and seven adults, including the gunman, dead at the school, and two children were pronounced dead later after being take to a hospital. Another adult was found dead at a related crime scene in Newtown, he said, bringing the toll to 28.
"Our hearts are broken today," President Barack Obama said in an emotional televised address to the nation.
"Evil visited this community today," Connecticut Governor Dannel Malloy told reporters.
Two law enforcement sources briefed on the investigation confirmed to Reuters the shooter had been identified as Adam Lanza, 20. Adam's brother Ryan Lanza was "either in custody or being questioned" at this hour, one of the sources said.
The New York Times reported that the gunman walked into a classroom where his mother was a teacher, shot his mother and then 20 students, most in the same classroom, b e fore shooting five other adults and killing himself. One other person was shot at the school and survived, the Times said.
The holiday season tragedy was the second shooting rampage in the United States this week and the latest in a series of mass killings this year, and was certain to revive a debate about U.S. gun laws.
Chaos struck as children gathered in their classrooms for morning meetings at Sandy Hook Elementary in Newtown, a city of 27,000 in Fairfield County, about 80 miles (130 km) northeast of New York City.
Police swarmed the scene and locked down the school, rushing children to safety, some of them bloodied. Distraught parents converged, frantically searching for their daughters and sons. Neighbors and friends wandered in shock, looking for information.
"It's hard to believe that anything like this could happen in this town," said resident Peter Alpi, 70, as he fought back tears. "It's a very quiet town. Maybe it's too quiet."
Hours later, Obama, wiping away tears and pausing to collect his emotions, mourned the "beautiful little kids between the ages of 5 and 10 years old" who were killed. He ordered flags flown at half staff at U.S. public buildings.
"As a country, we have been through this too many times," Obama said, ticking off a list of recent shootings.
"We're going to have to come together and take meaningful action to prevent more tragedies like this, regardless of the politics," Obama said in apparent reference to the influence of the National Rifle Association over members of Congress.
Obama remains committed to trying to renew a ban on assault weapons, White House spokesman Jay Carney said.
BLOODIED CHILDREN LEAVE SCHOOL
Vance said the shootings took place in two rooms of Sandy Hook Elementary School, which teaches children from kindergarten through fourth grade, roughly aged 5 to 10.
Witnesses reported hearing dozens of shots; some said as many as 100 rounds.
"It was horrendous," said parent Brenda Lebinski, who rushed to the school where her daughter is in the third grade. "Everyone was in hysterics - parents, students. There were kids coming out of the school bloodied. I don't know if they were shot, but they were bloodied."
Lebinski said a mother who was at the school during the shooting told her a "masked man" entered the principal's office and may have shot the principal. Lebinski, who is friends with the mother who was at the school, said the principal was "severely injured."
Lebinski's daughter's teacher "immediately locked the door to the classroom and put all the kids in the corner of the room."
Melissa Murphy, who lives near the school, monitored events on a police scanner.
"I kept hearing them call for the mass casualty kit and scream, 'Send everybody! Send everybody!'" Murphy said. "It doesn't seem like it can be really happening. I feel like I'm in shock."
The toll exceed that of one of the most notorious U.S. school shootings, the 1999 rampage at Columbine High School in Littleton, Colorado, where two teenagers killed 13 students and staff before killing themselves.
A girl interviewed by NBC Connecticut described hearing seven loud "booms" while she was in gym class. Other children began crying and teachers moved the students to a nearby office, she said.
"A police officer came in and told us to run outside and so we did," the unidentified girl said on camera.
In Hoboken, New Jersey, police cordoned off a block in connection with the Connecticut shootings, but an officer told reporters there was no body inside, contrary to an earlier media report.
The United States has experienced a number of mass shooting rampages this year, most recently in Oregon, where a gunman opened fire at a shopping mall on Tuesday, killing two people and then himself.
The deadliest came in July at a midnight screening of a Batman film in Colorado that killed 12 people and wounded 58.
The Connecticut shootings appear certain to trigger renewed debate over U.S. gun laws. New York Mayor Michael Bloomberg, founder of the advocacy group Mayors Against Illegal Guns, said it was "almost impossible to believe that a mass shooting in a kindergarten class could happen.
"We need immediate action. We have heard all the rhetoric before. What we have not seen is leadership - not from the White House and not from Congress," Bloomberg said. "That must end today."
In 2007, 32 people were killed at Virginia Tech university in the deadliest act of criminal gun violence in U.S. history.
In another notorious school shooting outside the United States, a gunman opened fire in 1996 in an elementary school in Dunblane, Scotland, and killed 16 children and an adult before killing himself.