Washington, Dec 17 (IANS): President Barack Obama vowed to use his office to prevent heinous acts like last week's massacre at an elementary school as he met the relatives of those killed trying to make sense of the senseless bloodshed.

Twenty-six people -- 20 of them children, ages 6 and 7 -- were killed Friday morning at Sandy Hook Elementary in New Town, Connecticut, about 60 miles north of New York City, before the shooter fatally shot himself.

Mourning the slain "beautiful little kids" a tearful Obama Sunday night regretted that, "as a country, we have been through this too many times" as he vowed to use his office to prevent such heinous acts in the future.

Addressing families of the slain in Newtown, Obama said: "In the coming weeks, I'll use whatever power this office holds to engage my fellow citizens, from law enforcement, to mental health professionals, to parents and educators, in an effort aimed at preventing more tragedies like this, because what choice do we have? We can't accept events like this as routine."

The president's remarks in Newtown marked the fourth time he's consoled the nation from a grieving community - the first three coming after shootings at Fort Hood, Texas; Tucson, Arizona; and Aurora, Colorado, events he mentioned in his speech.

Meanwhile, Adam Lanza, 20, has been positively identified as the killer gunman, Connecticut State Police Lt. J. Paul Vance said Sunday, according to CNN

The police spokesman also revealed that the shooter's mother, Nancy Lanza, is the woman found dead from "multiple gunshot wounds" in the Newtown home she lived in with her son.

While more details have emerged about Friday's massacre, authorities still don't have an explanation as to why it happened.

"We will and we are searching diligently and nonstop to attempt to answer that," Vance said.

The first authorities heard of the shooting at Newtown's Sandy Hook Elementary School came in a call around 9:30 a.m. Friday.

It was then Lanza got into the building -- not by being buzzed in, though a security system recently implemented by Principal Dawn Hochsprung, but by firing. Hochsprung was among the six adults killed.

Lanza used a Bushmaster AR-15 "assault-type rifle" to gun down children in two classrooms, according to Vance, then killed himself with a handgun. "Multiple magazines," each of which contained 30 bullets, were fired from the Bushmaster weapon in the school, he added.

"We surmise that it was during the second classroom episode that he heard responders coming and apparently at that (point) decided to take his own life," said Connecticut Governor Dannel Malloy on ABC.

All the victims died after being shot multiple times, said H. Wayne Carver II, Connecticut's chief medical examiner.

As to Lanza, the gunman, the few relatives and acquaintances who have talked publicly are at a loss to explain how this could have happened, CNN said.

He had no known criminal record. He visited a gun range, as did his mother, said ATF spokesperson Ginger Colbrun.