A man killed his mother at home and then opened fire Friday inside the elementary school, massacring 26 people, including 20 young children, as youngsters cowered in their classrooms and trembled helplessly to the sound of gunfire reverberating through the building.

The 20—year—old killer, carrying two handguns, committed suicide at the school, bringing the toll to 28, authorities said.

The rampage in the northeastern state of Connecticut was at least the fourth big shooting spree in five months in the United States. It was by far the deadliest of the year and most heart—wrenching.

The children were among the youngest victims of a mass shooting in recent history.

Frightened students who were rushed from the building by police were told to close their eyes. Children some crying, others looking frightened were escorted through a parking lot in a line, hands on each other’s shoulders.

Police shed no light on the motive for the attack. The gunman was believed to suffer from a personality disorder and lived with his mother in Connecticut, said a law enforcement official who was briefed on the investigation but was not authorized to publicly discuss it.

Law enforcement officials speaking on condition of anonymity said Adam Lanza killed his mother, Nancy Lanza, and then drove to the school in her car.

Authorities gave no details on exactly how the attack unfolded, but police radio traffic indicated the shooting lasted only a few minutes. State police Lt. Paul Vance said officers arrived instantaneously, immediately entered the school, searched it completely and found Lanza dead.

The attack at Sandy Hook Elementary School, just two weeks before Christmas, was the nation’s second—deadliest school shooting, exceeded only by the Virginia Tech university massacre in 2007 that left 32 dead.

This time, the victims were far smaller. Children told their parents they had heard bangs and, at one point, a scream over the intercom. Teachers ordered them to hide in closets or corners.

State police Lt. Paul Vance said 28 people in all were killed, including the gunman, and one person was injured.

Lanza’s older brother, 24—year—old Ryan was questioned, but a law enforcement official said he was not believed to have had any role in the rampage.

Investigators were searching his computers and phone records, but he told law enforcement he had not been in touch with his brother since about 2010.

Adam Lanza and his mother lived in a well—to—do part of Newtown where neighbors are doctors or hold white—collar positions at companies such as General Electric, Pepsi and IBM.

Initially three guns were found a Glock and a Sig Sauer, both pistols, inside the school, and a .223—caliber rifle in the back of a car, authorities said. A law enforcement official speaking on condition of anonymity said some of the guns used in the attack may have belonged to Lanza’s mother, who had legally purchased five weapons.

Later authorities recovered some more guns a Henry repeating rifle, an Enfield rifle and a shotgun. It was not clear exactly where those weapons were found.

The shooting shocked a tranquil community of 27,000 people in one of the wealthiest counties in the U.S.

Already this year, a gunman killed 12 people at a Colorado theater, and another gunman killed six people before killing himself at a Sikh temple in Wisconsin.

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