(CBS/AP)-- Investigators tried to figure out what led a bright but painfully awkward 20-year-old to slaughter 26 children and adults at a Connecticut elementary school, while townspeople sadly took down some of their Christmas decorations and struggled Saturday with how to go on.
The tragedy brought forth soul-searching and grief around the globe. Families as far away as Puerto Rico began to plan funerals for victims who still had their baby teeth, world leaders extended condolences, and vigils were held around the U.S.
Amid the sorrow, stories of heroism emerged, including an account of the Sandy Hook Elementary School principal who lost her life lunging at the gunman, Adam Lanza, in an attempt to overpower him.
Police shed no light on what triggered 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." He would not elaborate.
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.
The mystery deepened as Newtown education officials said they had found no link between Lanza's mother, Nancy Lanza, 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 on Friday.
A nurse who had been with the school for 15 years, told CBS News' Scott Pelley that no one knows Nancy Lanza and that she was not a staff teacher, after earlier reports said Nancy Lanza worked at the school. The nurse said its conceivable that Nancy Lanza was a substitute that she never met, but very unlikely. No other staff member the nurse has talked to has ever heard of Nancy Lanza. The nurse also knows of no connection between the shooter and the school.
Lanza shot to death his mother at the home they shared, then drove to the school in her car with at least three of her guns, forced his way inside and opened fire in two classrooms, authorities said. Within minutes, he killed 20 children, six adults and himself.
On Saturday, Chief Medical Examiner Dr. H. Wayne Carver said all the victims at the school were shot with a rifle, at least some of them up close, and all of them were apparently shot more than once. All six adults killed at the school were women. Of the 20 children, eight were boys and 12 were girls. All the children were 6 or 7 years old.
Asked how many bullets were fired, Carver said, "I'm lucky if I can tell you how many I found."
There is an unconfirmed report that Lanza was involved in an altercation with school staffers the day before the shooting. CBS News correspondent John Miller spoke to a law enforcement source regarding that report.
The source said what they are focused on was there was some kind of argument between people in the office, and the people in the office of that school are dead.
The source said the key is to figure out if Lanza was part of that, present for it or somehow involved. Additionally, the source said right now they have any indication Lanza was, but he said they have to run that out it make sure.
As for the weapons that appear to belong to Lanza's mother, Miller reported that Nancy Lanza must have gone through a lot of trouble in procuring them given the fact Connecticut has the toughest gun laws in the U.S.
He also reported speaking to a relative who said Nancy Lanza was worried about the defense of her home-- if there was a collapse of the economy, she wanted to have weapons on hand to defend them. It underscored the irony that those were the guns used by her own child to kill her and so many others.
The tragedy 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.
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.
The list of the dead was released Saturday, but in the tightly knit town, nearly everyone already seemed to know someone who died.
Among the dead: well-liked Principal Dawn Hochsprung, 47, who town officials say tried to stop the rampage and paid with her life; school psychologist Mary Sherlach, 56, who probably would have helped survivors grapple with the tragedy; a teacher thrilled to have been hired this year; and a 6-year-old girl who had just moved to Newtown from Canada.
"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."
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."
Authorities said 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.
The law enforcement officials insisted on anonymity because they were not authorized to discuss the unfolding investigation.
Acquaintances describe the former honor student as smart but odd and remote.
Olivia DeVivo, now a student at the University of Connecticut, recalled that Lanza always came to school toting a briefcase and wearing his shirt buttoned all the way up.
"He was very different and very shy and didn't make an effort to interact with anybody" in his 10th-grade English class, she said.
"You had yourself a very scared young boy who was very nervous around people," said Richard Novia, who was the school district's head of security and adviser to the high school's Tech Club, of which Lanza was a member. He added: "He was a loner."
Novia said Lanza had extreme difficulties relating to fellow students and teachers, as well as a strange bodily condition: "If that boy would've burned himself, he would not have known it or felt it physically."
Lanza would also go through crises that would require his mother to come to school to deal with. Such episodes might involve "total withdrawal from whatever he was supposed to be doing, be it a class, be it sitting and read a book," Novia said.
When people approached Lanza in the hallways, he would press himself against the wall or walk in a different direction, clutching his black case "like an 8-year-old who refuses to give up his teddy bear," said Novia, who now lives in Tennessee.
Even so, Novia said his main concern about Lanza was that he might become a target for teasing or abuse by other students, not that he might become a threat.
"Somewhere along in the last four years there were significant changes that led to what has happened Friday morning," Novia said. "I could never have foreseen him doing that."
Lanza's family was struggling to make sense of what happened and "trying to find whatever answers we can," his father, Peter Lanza, said in a statement late Saturday that also expressed sympathy for the victims' families.
Sandy Hook Elementary will be closed next week -- some parents can't even conceive of sending their children back, Leidlein said -- and officials are deciding what to do about the town's other schools.
Asked whether the town would recover, Maryann Jacob, a clerk in the school library who took cover in a storage room with 18 fourth-graders during the shooting rampage, said: "We have to. We have a lot of children left."