NEWTOWN, Conn. — The gunman behind the Connecticut elementary school massacre stormed into the building and shot 20 children at least twice with a high-powered rifle, executing some at close range and killing adults who tried to stop the carnage, authorities said Saturday.

He forced his way into the school by breaking a window, officials said. Asked whether the children suffered, Chief Medical Examiner Dr. H. Wayne Carver paused. “If so,” he said, “not for very long.”

The terrible details about the last moments of young innocents emerged as authorities released their names and ages — the youngest 6 and 7, the oldest 56. They included Ana Marquez-Greene, a little girl who had just moved to Newtown from Canada; Victoria Soto, a 27-year-old teacher who apparently died while trying to hide her pupils; and principal Dawn Hochsprung, who authorities said lunged at the gunman in an attempt to overtake him and paid with her life.

The tragedy has plunged Newtown into mourning and added the picturesque New England community of handsome Colonial homes, red-brick sidewalks and 27,000 people to the grim map of towns where mass shootings in recent years have periodically reignited the national debate over gun control but led to little change.

Faced with the unimaginable, townspeople sadly took down some of their Christmas decorations and struggled Saturday with how to go on. Signs around town read, “Hug a teacher today,” “Please pray for Newtown” and “Love will get us through.”

“People in my neighborhood are feeling guilty about it being Christmas. They are taking down decorations,” said Jeannie Pasacreta, a psychologist who was advising parents struggling with how to talk to their children.

School board chairwoman Debbie Leidlein spent Friday night meeting with parents who lost children and shivered as she recalled those conversations. “They were asking why. They can’t wrap their minds around it. Why? What’s going on?” she said. “And we just don’t have any answers for them.”

The tragedy brought forth soul-searching and grief around the globe. President Barack Obama planned to visit Newtown on Sunday. Families as far away as Puerto Rico planned funerals for victims who still had their baby teeth, world leaders extended condolences, and vigils were held around the U.S.

“Next week is going to be horrible,” said the town’s legislative council chairman, Jeff Capeci, thinking about the string of funerals the town will face. “Horrible, and the week leading into Christmas.”

Police shed no light on what triggered Adam Lanza, 20, to carry out the second-deadliest school shooting in U.S. history, though state police Lt. Paul Vance said investigators had found “very good evidence ... that our investigators will be able to use in painting the complete picture, the how and, more importantly, the why.”  

However, another law enforcement official, speaking on condition of anonymity, said investigators have found no note or manifesto from Lanza of the sort they have come to expect after murderous rampages such as the Virginia Tech bloodbath in 2007 that left 33 people dead.

Lanza shot to death his mother, Nancy Lanza, at the home they shared, then drove to the school in her car with at least three of her guns, forced his way in and opened fire, authorities said. Within minutes, he killed 20 children, six adults and himself.

Education officials said they had found no link between Lanza’s mother and the school, contrary to news reports that said she was a teacher there. Investigators said they believe Adam Lanza attended Sandy Hook Elementary many years ago, but they had no explanation for why he went there Friday.

Authorities said Adam Lanza had no criminal history, and it was not clear whether he had a job. Lanza was believed to have suffered from a personality disorder, said a law enforcement official who spoke on condition of anonymity.

Another law enforcement official, also speaking on condition of anonymity, said Lanza had been diagnosed with Asperger’s, a mild form of autism often characterized by social awkwardness. People with the disorder are often highly intelligent. While they can become frustrated more easily, there is no evidence of a link between Asperger’s and violent behavior, experts say.