Gunman, 20, believed to be autistic, killed teacher mom at home before driving to elementary school in her car and shooting TWENTY SIX dead including 20 children

• The shooter, Adam Lanza, 20, is confirmed dead and body still inside the school
• Brother Ryan, 24, is in custody and being questioned
• One teacher said masked gunman started firing out shots from principal's office and then his mom Nancy's kindergarten classroom shortly after 9.30am
• Mom was killed at home in Newtown, which was once voted one of America's safest places to live
• One student said there were bullets whizzing by him in the hallway
• Female principal and school psychologist believed to have been targeted
• Moved to tears, President Obama says 'our hearts are broken today'
• No positive IDs but parents who have not been reunited with their children are assuming the worst
• Flags around America being flown at half mast

The gunman who today slaughtered 26 people including 20 children used his teacher mother's own guns to shoot students in her kindergarten class during his horrific killing spree at a Connecticut elementary school, it was revealed tonight.
Adam Lanza, 20, who is said to have a personality disorder, was carrying a .223 rifle and two handguns when he entered the Sandy Hook Elementary school shortly after 9.30am and started gunning people down - after he shot his mother Nancy, 52, in her face at her nearby home.
Witnesses say he was going from room-to-room shooting people after first killing the principal Dawn Hochsprung and psychologist execution-style in the main office.
Officials said most of the slaughter occurred in two classrooms, and one entire class is unaccounted for.

Parents who have not been united with their children are assuming the worst. One witness told WCBS: '(Police) just told us everyone presumed missing is in the school and they are dead.'

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Adam Lanza, 20, shot his teacher mother before driving to her elementary school and shooting 26 people including 20 children

Ryan Lanza is seen being led away from his Hoboken home in New Jersey to be questioned by police over this morning's shooting

Ryan Lanza is escorted to a car outside his home in Hoboken by law enforcement in connection with an elementary school shooting this morning

Traumatized students were seen being led out of the school crying and holding hands

The families of victims grieve near Sandy Hook Elementary School, where teacher Nancy Lanza's son Adam, 20, opened fire and killed 20 children and six adults

President Obama openly wept today as he spoke of the mindless shooting of 29 people, including 22 children, at Sandy Hook Elementary school this morning saying, 'Our hearts are broken today'

Heavily armed Connecticut State troopers and FBI agents swarmed to the scene at Sandy Hook High School

People arrive for a prayer vigil at the Newtown United Methodist Church following a shooting at the Sandy Hook Elementary School

Map of area surrounding Sandy Hook Elementary School in Newtown, Connecticut, where a gunman killed at least 26 people, 20 of them small children

THE .223-CALIBER RIFLE: CHOICE OF GUN USED IN THREE OF 2012'S MASS SHOOTINGS

The shooter in the Connecticut elementary massacre was armed with two handguns and a .223-caliber rifle.
The caliber has become popular as 'self-defense' ammunition - but it has also been used in two of this year's mass shootings.
The .223 is nearly the same cartridge as the 5.56mm ammunition used in U.S. military M-16 and M4 rifles.
The popular civilian version of the military weapons - the AR-15 - fires the .223 cartridge.
AR-15 rifles - which are semiautomatic and can fire from magazines of up to 100 rounds - were used by the gunmen in the Aurora, Colorado, movie theater massacre and the shooting at an Oregon shopping mall on Tuesday.
Twelve people were killed in Colorado. Three died in Oregon, including the gunman.
The light weight, accuracy and long range of the .223 cartridge make it ideal for self defense and military rifles.
Sales of AR-15-style rifles have spiked in the United States since the September 11 terrorist attacks.
Gun owners have bought millions of them in recent years over fears that new gun regulations will make them harder purchase.
As many as 30 percent of the nation's gun owners have an AR-15 or similar semiautomatic rifle.
The vast majority are chambered in the .223 ammunition.
The most recent .223 designs, such as the Winchester .223 PDX1 projectile have a split core.
This ensures that the bullet has a maximum impact on a human target, penetrating and then fragmenting causing a devastating cavity wound.

Students described being ushered from their classrooms hand-in-hand, with their eyes closed, to the safety of a nearby fire station as police converged on the school.
Adam's brother Ryan, 24, who was originally thought to have been the shooter, is being questioned by police after he was arrested at his home in Hoboken, New Jersey.
He was on a bus on his way home from work when he was being named as the gunman and posted on Facebook that it wasn't him.
He told a friend he believed his mentally disabled brother did it. Adam is believed to be autistic.
Another relative told ABC Adam had been 'obviously not well' and Beth Israel, tonight tweeted that her daughter went to school with him and he was 'troubled for a long time'.
Alex Israel spoke to CNN about how she went to school with Adam and she described him as fidgety, and a quiet loner who kept to himself.
She also said he was a highly intelligent student, 'above the rest of us'.
But she said he was never violent.
She tweeted earlier in the day that he was 'crazy'.
The gunman's father Peter Lanza, who is divorced from his wife, lives in Stamford, Connecticut, and declined to comment this evening after police performed a welfare check on him.
Neighbors said he recently remarried.
Mr Lanza learned of the tragic and senseless massacre by reporters who had flocked to his home.
He arrived shortly after police left and asked what the problem was.
The Stamford Connecticut said his expression shifted from patient to surprise to horror.
Newtown was once named one of the safest places to live in America and before this morning, there had been one murder in a decade.
The President addressed a stunned nation five hours after the shooting and openly wept as he spoke of the mindless shooting saying: 'Our hearts are broken today.'
Seldom has a head of state expressed greater public emotion in modern times.
Obama struggled for words, pausing several times as he wiped away tears saying, 'This evening, Michelle and I will...hug our children a little tighter, and we'll tell them that we love them.'
Lanza is believed to have shot himself at the scene, according to the New York Times.

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