Hundreds of mourners descended on a church in Newtown, Connecticut Friday night to grieve the deaths of 20 young children and six adults killed by a lone gunman at a local elementary school.

Many other mourners gathered outside the packed church, as the community and the nation sought to absorb the scope of the tragedy. Governor Dannel Malloy said simply “evil visited this community today.”

Earlier, in Washington, a tearful U.S. President Barack Obama addressed the American public, saying “our hearts are broken” by the deaths.

His address came hours after horror and mayhem struck at the school in Newtown, a small community 130 kilometers northeast of New York. The president said, “The majority of those who died today were children — beautiful little kids between between the ages of five and 10 years old. They had their entire lives ahead of them….”

Vigils were also organized in other cities across the country.

Witnesses say the 20-year-old gunman dressed in black military fatigues entered the school at mid-morning, opening fire on children and their teachers in two rooms. A military assault rifle was later found in the gunman's car. The shooter, identified as Adam Lanza, died at the scene of a self-inflicted gunshot. Two semi-automatic handguns were found nearby.

Authorities say the shooter killed his mother at her home in the town before driving her car to the school.

Police have not established a motive for the killings.

The gunman's brother was taken by police for questioning late Friday in New Jersey. Police say he is cooperating in the probe.

President Obama called the shooting a “heinous crime,” and said “as a country we have been through this too many times.” He then listed a string of recent mass shootings, including those at a temple in Wisconsin, a movie theater in Colorado and a shopping mall in Oregon. He said “we're going to have to come together and take meaningful action to prevent more tragedies like this, regardless of the politics.”

Video from the crime scene showed children being rushed from the school single file, people hugging, and frantic parents either waiting for word on their children or hugging them once found. It took several hours before the full scope of the tragedy became public.

When it did, reports of heroism surfaced as well. In one instance, a teacher herded her entire first grade class into a bathroom, locked the door, and cowered alongside the children until help arrived.

When police arrived on the scene, she made them slide identification under the door before she would open it.