(Update) — Connecticut state police report 27 people were killed today at school in Newtown, including the gunman and 20 schoolkids.

A law enforcement official identifies the shooter as 20-year-old Adam Lanza. His mother was a teacher at the school. Media reports she was not at the school, but was killed at her home.

The official says Lanza’s older brother is being held for questioning after he was arrested in New Jersey.

Witnesses say many of the students at Sandy Hook Elementary School found out about the mass shooting via the school’s loudspeakers, which someone in the principal’s office turned on during an argument between the gunman and the principal. Many teachers were able to lock their doors upon hearing it.

State police now confirm 27 people are dead, 20 students, ages five to ten, and seven adults, including the gunman. The 20-year-old gunman’s mother was a teacher at the school, and officials say many of the students were killed in her classroom. The gunman’s 24-year-old brother has been arrested in New Jersey.

A tearful President Barack Obama says the country’s leaders must “take meaningful action” — regardless of politics — in response to the mass shooting at a Connecticut elementary school. Speaking to the nation today from the White House, the president paused repeatedly, struggling to keep his composure while speaking of the children — ages 5 to 10 — who had died and the life milestones they now would miss.

Shortly before speaking, Obama ordered that U.S. flags be flown at half-staff on public grounds through Tuesday.

NEWTOWN, Conn. (AP) — An official with knowledge of a shooting at a Connecticut elementary school says 27 people are dead, including 20 children.

The official spoke on condition of anonymity because the investigation is still under way.

State police Lt. Paul Vance says only that staff and students at Sandy Hook Elementary School in Newtown are among the victims. He says the shooter was dead in the school.

Vance says Newtown police called state police around 9:40 a.m. A SWAT team was among the throngs of police to respond to the school, about 60 miles northeast of New York City.

Photos from the scene showed young students — some crying, others looking visibly frightened — being escorted by adults through a parking lot in a line, hands on each other’s shoulders.