By Holly Yan
(CNN) -- At a time when Newtown should be reveling in holiday cheer, the grief-stricken community will begin the grim task of lowering 20 little coffins into the ground.
Six-year-old Jack Pinto, whose love for sports ran the gamut but none so deep as football, will be laid to rest Monday.
Noah Pozner, another 6-year-old, whose family said he could get what he wanted just by batting his long eyelashes, will also be buried.
And the heartbreaking ritual will continue for days.
Jessica Rekos on Tuesday. Benjamin Wheeler on Thursday. Madeleine Hsu, Friday. All of them 6 years old.
But even after the families of the 20 children and six educators killed at Sandy Hook Elementary school say their last goodbyes, it's unlikely the tight-knit community will ever be the same.
"It's incomprehensible, the pain here," resident Darla Henggeler said. "You can't imagine. We're still in shock. I can't let my heart go there because it's so overwhelming.
"I think once it settles in, I think my heart will break."
Obama: "These tragedies must end."
In Newtown High School's packed auditorium, President Barack Obama recited the names of the children slain at Sandy Hook and offered his condolences to the community.
"All across this land of ours, we have wept with you," Obama said Sunday night.
He also said the country has failed to do everything it can to protect youths from such immense tragedy.
"Can we honestly say we're doing enough to keep our children -- all of them -- safe from harm?" Obama said, adding that "if we don't get that right, we don't get anything right."
"If we're honest with ourselves, the answer is no."
He noted this is the fourth time in the past two years that a mass shooting has united the country in despair. Tucson, Aurora, Oak Creek, Newtown.
"These tragedies must end. And to end them, we must change."
The president didn't mention specific steps, but promised 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."
His call to action capped an emotional prayer service at Newtown High, in which local leaders of several religions -- a Jewish rabbi singing a prayer, a Muslim man choking back tears, and several Christian leaders offering perspective -- attempted to comfort a shattered community. Nine hundred watched in the school's auditorium, including several children toting teddy bears.
Shortly before Obama's remarks, the grassroots group Newtown United launched "to create meaningful dialogue, both locally and beyond, around the issues that led to this this senseless act of violence."
The group plans to send a delegation to Washington on Tuesday to meet with the Brady Campaign to Prevent Gun Violence as well as families from July's movie theater massacre in Aurora, Colorado.
Clues on what happened, but not why
It's possible no one will ever know what led Adam Lanza to kill his mother, Nancy, in their home before taking her guns and raining hell on Sandy Hook Elementary School and eventually killing himself.
Investigators now know the gunman used "an assault weapon" to "literally (shoot) an entrance into the building," Connecticut Gov. Dannel Malloy said Sunday.
The nightmare worsened as he moved through Sandy Hook's halls.
Using a Bushmaster AR-15 "assault-type rifle," the 20-year-old fired multiple magazines -- each of which contained 30 bullets -- to gun down the adults and children in two classrooms, Connecticut State Police Lt. J. Paul Vance said.
He then took out a handgun and shot himself in a classroom as officers approached, officials said.
All the victims were shot between three and 11 times.
"This probably is the worst I have seen or the worst that I know of any of my colleagues having seen," said Connecticut chief medical examiner H. Wayne Carver II, who conducted autopsies on seven victims.
The perpetrator had no known criminal record.
His father, Peter Lanza, released a statement Saturday saying his family is "grieving along with all those who have been affected by this enormous tragedy."
"Our hearts go out to the families and friends who lost loved ones and to all those who were injured," the father said. "We are in a state of disbelief and trying to find whatever answers we can. We, too, are asking why."
Relatives carry on the victims' voices
As more details about the 20 children and six educators emerge, so do stories of heroism and joyous memories of lives cut far too short.
When the gunfire rang out, 27-year-old Victoria Soto scrambled to move her students away from her first-grade classroom door and shielded them in the corner of the room.
It's not surprising that Soto would risk her life to save others, her mother said.
"She was truly selfless," Donna Soto said Sunday. "She would not hesitate to think to save anyone else before herself and especially children. She loved them more than life."
Six-year-old Emilie Parker was a budding young artist who would have been the first to console the victims had she herself not been killed, her father said.
"She loved to use her talents to touch the lives of everyone that she came in contact with," Robbie Parker said. "She always carried around her markers and pencils so she never missed an opportunity to draw a picture or make a card for those around her."
Emilie's father also offered his condolences to all the families affected.
"This includes the family of the shooter," he said. "I can't imagine how hard this experience must be for you, and I want you to know that our family, and our love and support goes out to you as well."
Noah, one of the boys who will be laid to rest Monday, loved playing with his siblings -- especially his twin sister. They still don't know know how their brother passed away, Noah's aunt said.
"How do you tell them that's how their brother died?" Haller asked. "It's the unthinkable really."
It's just as unbearable as the thought of a parent burying a child.
CNN's Susan Candiotti and Wayne Drash contributed to this report from Newtown, Connecticut. CNN's Dana Ford, Greg Botelho, David Ariosto, Candy Crowley and Chuck Johnston also contributed to this report.