A small town in the northeastern United States is beginning the grim task of holding the first funerals for the 20 children and six adults killed in a shooting rampage at an elementary school.

Funerals for two six-year-old boys are being held Monday, the first for those gunned down at the Sandy Hook Elementary school in Newtown, Connecticut. The children killed in the attack Friday were six and seven years old.

A state police official said the school is still an active crime scene and detectives are working 24 hours a day on the case. He said a secondary site is also being held as a crime scene. He said two adults were shot and survived the attack.

President Barack Obama joined mourners in Newtown Sunday night, telling those gathered for a vigil that they are not alone in their grief and that the nation is left with hard questions.

He has vowed to use all of his power to prevent another such tragedy, noting the rampage was the fourth mass shooting since the start of his presidency, almost four years ago.

“We can't tolerate this anymore. These tragedies must end, and to end them we must change. We will be told that the causes of such violence are complex, and that is true. No single law, no set of laws can eliminate evil from the world and prevent every single act of violence in our society. But that can't be an excuse for inaction.”

Schools in the district are expected to re-open Tuesday, except for Sandy Hook Elementary, which police say will remain closed indefinitely.

The adult victims were women and included the school's principal, Dawn Hochsprung, who reportedly tried to stop the shooter, and teacher Victoria Soto, who is credited with saving some of her students by putting herself between them and the attacker. The shooter reportedly killed his mother at their home.

Authorities have identified the killer as Adam Lanza, who is described as a quiet and socially awkward, but very bright 20-year-old. Officials say Lanza died at the scene of a self-inflicted gunshot wound.

Connecticut's chief medical examiner said the victims were killed at close range by multiple gunshots from an assault-style rifle. According to law enforcement officials, Lanza's mother legally owned the rifle used in the massacre as well as two handguns reportedly found near his body.

Friday's attack was the second worst school shooting in U.S. history. The worst occurred in 2007, when a gunman killed 32 people at Virginia Polytechnic Institute and State University in Blacksburg, Virginia. Before that, the deadliest U.S. school shooting was the 1999 rampage at Columbine High School in Littleton, Colorado, where two teenagers killed 13 students and staff before killing themselves.