Police in Connecticut have said the gunman who killed 20 children at a school in America was "remote" and may have suffered from a personality disorder.
Adam Lanza was a former pupil at Sandy Hook Elementary school and killed himself after the shootings.
Officers have released recordings of their calls which become more and more desperate as the situation becomes clear.
The head of the Connecticut primary school was among the victims, an official said today.
Sandy Hook Elementary School principal Dawn Hochsprung was among the 27 people the gunman shot dead, according to Gerald Stomski, a councillor in nearby Woodbury.
Mr Stomski said Ms Hochsprung was a school principal in Woodbury until a few years ago, adding that she had “an extremely likable style”.
She had been head at Sandy Hook Elementary since 2010, and frequently tweeted photos from her job and wrote upbeat tweets about what was going on at the school.
More hauntingly, several publications report she wrote a letter before the school year outlining new safety measures – including locked doors during school hours.
Police said Lanza killed his mother at their home before driving her car to the school where he went on the rampage.
Lanza’s mother Nancy was a teacher at Sandy Hook, where the 20-year-old killed another 26 people, including 20 children, before shooting himself dead.
State police said 18 children were found dead at the school and two died later in hospital. Six adults were found dead at the scene. They said the shootings occurred in one section of the school but did not give details.
In New Jersey, Lanza’s older brother Ryan, 24, of Hoboken, told investigators his brother was believed to suffer from a personality disorder and be “somewhat autistic”.
Three guns were found at the scene of the massacre – a Glock and a Sig Sauer, both pistols, and a .223-calibre rifle. The rifle was recovered from the back of a car at the school, and the pistols were found inside the school. Detectives suggested they might have belonged to Ms Lanza.
Hundreds of people attended a church vigil in Connecticut last night to remember the victims of the shooting.
With the St Rose of Lima church in Newtown filled to capacity, hundreds of people stood outside, some holding hands in circles and saying prayers, while others lit candles and sang Silent Night.
State governor Dannel P Malloy was among the speakers at the service.