Escorted by his family member, a child (R) leaves the Sandy Hook Elementary School after the fatal school shooting in Newtown, Connecticut, the United States, Dec. 14, 2012. [Xinhua]

A shooting incident on Friday morning in an elementary school in Newtown of the Connecticut State of the United States killed 20 children and six adults, and another one was injured.

Eighteen children were pronounced dead on the scene at the Sandy Hook Elementary School in Newtown, and two more at the hospital, Connecticut State Police spokesman Lieutenant Paul Vance told a press briefing.

The killer was also found in the school, said Vance, adding the shooting occurred at a concentrated area in two rooms at the school.

Another death was reported at a secondary scene in Newtown, bringing the death toll to 28.

Another person was injured in the shooting but survived, Vance said. Media reports said as the injured was the vice principal.

Earlier reports said the shooter was 24-year-old Ryan Lanza. Police later confirmed the killer was his brother Adam Lanza, 20. Ryan Lanza was reportedly in police custody.

Reports said Adam's mother, Nancy Lanza, is also among those found dead in the school, but it was not confirmed by the police.

In a statement from the White House briefing room, President Barack Obama said the United States needs to take "meaningful action," regardless of politics, to prevent more tragedies, noting the country has seen too many shootings throughout the years.

Obama, in choked voice, said the nation was "heartbroken" over the deaths of so many innocent children. He described the shooting as "senseless acts of violence."

"The majority of those who died today were children, beautiful little kids between the ages of five and ten years old," said Obama. "They had their entire lives ahead of them, birthdays, graduations, weddings, kids of their own.

He ordered U.S. flags on the White House, official building and military facilities to half staff to honor the victims of the shooting incident.

Some news media reported the shooter also killed one of his brothers in New Jersey, but the report was disputed by police.

So far, the motive of the shooting incident remains unknown. Police said investigation process takes time.

The death toll of the incident, which happened three days following the killing of three people, including the gunman, in a mall shooting in the U.S. state of Oregon, is the highest from a school shooting in U.S. history since a gunman killed 32 people at Virginia Tech in 2007.

At Columbine High School in Littleton, Denver, two teens killed 13 people and wounded 24 in 1999.