A heavily armed gunman opened fire inside a Connecticut elementary school on Friday, killing 26 people, including 20 children, police said, in one of the worst mass shootings in U.S. history.

The gunman - who according to a media report carried four weapons and wore a bullet-proof 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 at a hospital. Another adult was found dead at a related crime scene in Newtown, he said, bringing the toll to 28.

The New York Times reported that the gunman, believed to be in his 20s, walked into a classroom where his mother was a teacher, shot his mother and then 18 students in the room before shooting five other adults and killing himself.

“Our hearts are broken today,” President Barack Obama said in an emotional televised address to the nation.

Chaos struck as children gathered in their classrooms for morning meetings at Sandy Hook Elementary in Newtown, a city of about 27,000 in northern Fairfield County, about 45 miles southwest of Hartford and 80 miles northeast of New York City.

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.

READ ON: 28 dead, including 20 students, in CT school shooting
LIVE COVERAGE: Newtown, Connecticut school shooting

It may have sounded good on paper: Win re-election, fly to Asia, soak up the adulation of fellow world leaders, then go home with at least a few tangible rewards to show for a legacy-shaping U.S. strategic shift eastwards. But U.S. President Barack Obama’s first post-election trip abroad did not work out exactly according to plan. To be sure, he had a chance to tout a foreign policy success with a landmark visit to the former pariah state of Myanmar, demonstrate he was serious about improved U.S. ties with nations in China’s backyard and take in a travelogue’s worth of iconic religious and cultural sights. But even as Obama sought to strengthen his administration’s “Asia pivot,” he came face-to-face with the tough realities of what it will take to counter China’s influence in the region. At the same time, he found his attention constantly diverted back to the world’s biggest hotspot, the Middle East, where a Gaza crisis raged on. READ ON: Obama’s Asia tour doesn’t go exactly according to plan
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It may have sounded good on paper: Win re-election, fly to Asia, soak up the adulation of fellow world leaders, then go home with at least a few tangible rewards to show for a legacy-shaping U.S. strategic shift eastwards.

But U.S. President Barack Obama’s first post-election trip abroad did not work out exactly according to plan.

To be sure, he had a chance to tout a foreign policy success with a landmark visit to the former pariah state of Myanmar, demonstrate he was serious about improved U.S. ties with nations in China’s backyard and take in a travelogue’s worth of iconic religious and cultural sights.

But even as Obama sought to strengthen his administration’s “Asia pivot,” he came face-to-face with the tough realities of what it will take to counter China’s influence in the region.

At the same time, he found his attention constantly diverted back to the world’s biggest hotspot, the Middle East, where a Gaza crisis raged on.

READ ON: Obama’s Asia tour doesn’t go exactly according to plan

FLASH: CIA director David Petraeus has resigned, according to a U.S. intelligence source

A second intelligence source says Petraeus met with President Obama on Thursday. The White House says it will let Petraeus address resignation reports, adding that Obama will likely have a statement later.

More soon at Reuters.com.

FLASH: MSNBC, CBS project Barack Obama wins re-election as U.S. President. [Live coverage] Photo: U.S. President Barack Obama greets supporters on his last night of campaigning in downtown Des Moines, Iowa, November 5, 2012. An emotional President Obama ended his final campaign on Monday in Iowa, the place that launched his first White House bid and that could hold the key to his political future. [REUTERS/Larry Downing]
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FLASH: MSNBC, CBS project Barack Obama wins re-election as U.S. President. [Live coverage]

Photo: U.S. President Barack Obama greets supporters on his last night of campaigning in downtown Des Moines, Iowa, November 5, 2012. An emotional President Obama ended his final campaign on Monday in Iowa, the place that launched his first White House bid and that could hold the key to his political future. [REUTERS/Larry Downing]

FLASH: MSNBC projects Obama wins re-election as U.S. president

reuterspolitics: CNN projects Obama wins Vermont, Romney wins Kentucky in presidential race. Polls now closed in GA, SC, VT, VA, portions of FL, NH, remainder of IN, KY. Polls close at 7:30pm ET in OH, NC, WV.LIVE COVERAGE: The 2012 U.S. Presidential DebatePhoto: A woman dressed as the Statue of Liberty poses for photographs during an election party during the U.S. Presidential election at the U.S. Embassy in London, November 6, 2012. [REUTERS/Neil Hall] For the latest news on the U.S. election, follow Reuters Politics
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reuterspolitics:

CNN projects Obama wins Vermont, Romney wins Kentucky in presidential race.

Polls now closed in GA, SC, VT, VA, portions of FL, NH, remainder of IN, KY. Polls close at 7:30pm ET in OH, NC, WV.

LIVE COVERAGE: The 2012 U.S. Presidential Debate

Photo: A woman dressed as the Statue of Liberty poses for photographs during an election party during the U.S. Presidential election at the U.S. Embassy in London, November 6, 2012. [REUTERS/Neil Hall]

For the latest news on the U.S. election, follow Reuters Politics

Reuters live blog poll: Who made the stronger arguments during the final presidential debate? Results: 63% Obama, 33% Romney, 5% Draw LIVE COVERAGE: The 2012 presidential campaign
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Reuters live blog poll: Who made the stronger arguments during the final presidential debate?

Results: 63% Obama, 33% Romney, 5% Draw

LIVE COVERAGE: The 2012 presidential campaign

Vote: Who made the stronger arguments during the final presidential debate?

President Barack Obama aggressively challenged Republican candidate Mitt Romney on jobs, energy and Libya in their second debate on Tuesday as the Democrat tried reclaim the momentum in a tight White House race. Obama was much sharper and more energetic than in their first debate two weeks ago, when his listless performance was heavily criticized and gave Romney’s campaign a much-needed boost. The incumbent fought back against Romney’s accusations that he had played down the attack by Islamist militants in Libya last month that killed four Americans, including the U.S. Ambassador Chris Stevens. “I’m the president and I’m always responsible,” Obama said. The two men argued over whether the White House had described the Benghazi attack as terrorism or not, with Obama saying he had in fact called it an act of terror when he spoke in the Rose Garden the following day. READ ON: Obama takes offensive against Romney in debate rematch
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President Barack Obama aggressively challenged Republican candidate Mitt Romney on jobs, energy and Libya in their second debate on Tuesday as the Democrat tried reclaim the momentum in a tight White House race.

Obama was much sharper and more energetic than in their first debate two weeks ago, when his listless performance was heavily criticized and gave Romney’s campaign a much-needed boost.

The incumbent fought back against Romney’s accusations that he had played down the attack by Islamist militants in Libya last month that killed four Americans, including the U.S. Ambassador Chris Stevens.

“I’m the president and I’m always responsible,” Obama said.

The two men argued over whether the White House had described the Benghazi attack as terrorism or not, with Obama saying he had in fact called it an act of terror when he spoke in the Rose Garden the following day.

READ ON: Obama takes offensive against Romney in debate rematch

In response to an advertisement released on the Internet by the Obama for America campaign, Sesame Workshop released the following statement today:

“Sesame Workshop is a nonpartisan, nonprofit organization and we do not endorse candidates or participate in political campaigns. We have approved no campaign ads, and as is our general practice, have requested that the ad be taken down.”

LIVE BLOG: Reuters coverage of the 2012 election