'It was my brother. I think my mother is dead. Oh my God': Moment accountant sibling of school shooter saw himself named as killer on TV in case of mistaken identity

• Gunman who opened fire at Sandy Hook Elementary School on Friday morning named as Adam Lanza, 20, by police sources
• Lanza died at the scene 'and was carrying brother's ID'
  
• Ryan Lanza works as an accountant at Ernst and Young in the company's Times Square office
  
• Brother, Ryan Lanza, forced to defend himself on Facebook
  

By LYDIA WARREN and BETH STEBNER

PUBLISHED: 19:49, 14 December 2012 | UPDATED: 05:21, 15 December 2012

Ryan Lanza was working at his desk at the Ernst and Young when he saw CNN reporting that he had killed 30 people at an elementary school in Connecticut.

It was the moment a stunned Ryan realized what his brother, Adam, might have done.

Lanza told his boss that: 'I need to go.' Then he walked out from Times Square office of the tax real-estate group, according to a co-worker who spoke to MailOnline on condition of anonymity.

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Custody: Ryan Lanza is taken away by police after they found him at his Hoboken New Jersey home

Mysteries: Police began questioning Ryan Lanza Friday night

Thirty minutes later, New York cops stormed in the office.  

Between leaving the office and being taken in for questioning, Lanza defended himself in a series of bizarre Facebook posts after he was mistakenly named as the killer when his ID was reportedly found at the scene.

Lanza, 24, seemed unaware that his younger brother, Adam Lanza, had gunned down 20 children and six adults at Sandy Hook Elementary School, in Newtown before taking his own life.

'Everyone shut the f*** up it wasn't me,' he insisted on his Facebook page on Friday. 'I'm on the bus home now it wasn't me. IT WASN'T ME I WAS AT WORK IT WASN'T ME.'

Brett Wilshe, a friend of Ryan Lanza's, told the AP that he sent Ryan a Facebook message Friday asking what was going on and if he was alright. 

According to Wilshe, Lanza's reply was something along the lines of: 'It was my brother. I think my mother is dead. Oh my God.' 

Questioning: Ryan Lanza is led away for questioning by police after his brother is named as the killer

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

Adam Lanza attended Newtown High School, and several local news clippings from recent years mention his name among the school's honor roll students. 

A neighbor in Newtown, Rhonda Cullens, said she knew Nancy Lanza from monthly get-togethers the neighborhood women had a few years back for games of bunco, a dice game. 'She was a very nice lady,' Cullens told the Associated Press.

'She was just like all the rest of us in the neighborhood, just a regular person.' Cullens recalled that Lanza liked to garden and to make her house look nice for the holidays. 

Lanza joked, though, that no one noticed because the house was out of view, up a hill, she said. 

The Associated Press said the mix-up came after an official mistakenly transposed the brothers' first names, while a New Jersey reporter said Ryan Lanza told him the killer may have had his ID.

He is now being questioned by police in Hoboken, New Jersey, but police said he is not a suspect. 

Adam Lanza, 20, was dressed in black military gear and a bullet proof vest when he opened fire in the principal's office and then moving to a kindergarten classroom where his mother, Nancy, taught.

Sources told the New York Post that Lanza had 'had a dispute with' his mother, who was found dead at her home. He then drove to the school in her car and gunned down her kindergarten class, Fox reported.

Lanza died of a self-inflicted gun wound at the scene. The Newtown Patch reported that he may have been developmentally disabled.

Escorted: Ryan Lanza is driven from One Police Plaza in Hoboken, New Jersey

Implicated: There had been confusion over the identity of the gunman, Adam Lanza, as he was carrying identification with his brother's name, Ryan Lanza (pictured left and right)

Led away: Ryan Lanza has not been named as a suspect but was taken away in handcuffs

Search: Police enter the apartment building in Hoboken, New Jersey where accused Ryan Lanza lives

The Associated Press reported that Lanza's girlfriend and another friend are missing in New Jersey.

His father, Peter Lanza, who was divorced from Nancy, declined to comment at his home in Stamford on Friday when reporters told him about his connection to the shooting.

Police surrounded a Hoboken apartment, believed to be the home of Ryan Lanza, on Grand Street on Friday afternoon.

According to sources, Adam Lanza drove to the scene of the shootings in his mother's car and opened fire at 9.41am on Friday.

Confusion: After police mistakenly identified the killer as Ryan Lanza, he fought back on his Facebook page

Three guns were found at the scene - a Glock and a Sig Sauer, both pistols - and a .223-caliber rifle. The rifle was recovered from the back of a car at the school. The two pistols were recovered from inside the school.

The identities of the other victims have not yet been released but include the school principal, Dawn Hochsprung, and psychologist. Two of the children died while on the way to hospital.

Robert Licata said his six-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.'

Horror: Crying children are led from the school where the gunman opened fire on Friday morning

Fears: A woman waits to hear about her sister, a teacher, following a shooting at Sandy Hook Elementary School. Children and parents have recounted the terrifying scene inside the buildings

Horror: Young children wait outside the school as police and paramedics swarm the area

Stephen Delgiadice said his eight-year-old daughter heard two big bangs and teachers told her to get in a corner. His daughter was fine.

'It's alarming, especially in Newtown, Connecticut, which we always thought was the safest place in America,' he said.

A dispatcher at the Newtown Volunteer Ambulance Corps said a teacher had been shot in the foot and taken to Danbury Hospital.

Andrea Rynn, a spokeswoman at the hospital, said it had three patients from the school but she did not have information on the extent or nature of their injuries.

Questions: The killer opened fire in Newtown, Connecticut and his brother is being quizzed in New Jersey

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

'Everyone was just traumatized,' he said.

The shooting is the latest in a series of high-profile gun crimes in American schools and colleges, that is especially shocking given the age of the students involved.