Priscilla and Randy Bock, arriving with their 15-year-old special needs son, James, expressed misgivings. "I was not sure we wanted him going," Priscilla Bock said. "I'm a mom. I'm anxious."
"Is there ever a right day? I mean, you just do it, you know, just get them back to school," said Peter Muckell as he took 8-year-old daughter Shannon, a third-grader, to Hawley Elementary.
At one Newtown school, students found some comfort from Ronan, an Australian shepherd therapy dog from Good Dog Foundation in New York.
Owner Lucian Lipinsky took the dog to a fifth-grade science and math class where students were having difficulty coping with the tragedy. Most started smiling immediately.
Lipinsky told the students they could whisper their secrets into Ronan's ear.
"It's pretty amazing how a lot of kids will just go whisper in his ear and tell them their secret, and, of course, he doesn't tell anyone," Lipinsky said. "He's a very good dog."
Authorities say the horrific events of Friday began when Lanza shot his mother, Nancy, at their home, then took her car and some of her guns to the nearby school, where he broke in and opened fire, killing 20 children and six adults before shooting himself.
A Connecticut official said the mother, a gun enthusiast who practiced at shooting ranges, was found dead in her pajamas in bed, shot four times in the head with a .22-caliber rifle.
Investigators have found no letters or diaries that could explain the attack, even as more fragments of Lanza's life emerged.
As a teenager, Lanza was so painfully shy that he would not speak or look at anyone when he came in for a haircut about every six weeks, always accompanied by his mother, said stylists in the Newtown hair salon Lanza frequented.
Cutting Adam Lanza's hair "was a very long half an hour. It was a very uncomfortable situation," stylist Diane Harty said, adding that she never heard his voice.
Another stylist, Jessica Phillips, said Nancy Lanza would give her son directions about what to do and where to go. He would move only "when his mother told him to," said a third stylist, Bob Skuba.
Meanwhile, the tragedy continued to reverberate around America.
Lanza is believed to have used a Bushmaster AR-15-style rifle, a civilian version of the military's M-16. It is similar to the weapon used in a recent shopping mall shooting in Oregon and other deadly attacks around the U.S.
Private equity firm Cerberus Capital Management announced Tuesday it plans to sell its stake in Freedom Group, maker of the Bushmaster rifle, following the school shootings.
Cerberus said in a statement that it was deeply saddened by Friday's events and will hire a financial adviser to help with the process of selling its Freedom Group interests.
In Pittsburgh, Dick's Sporting Goods said it is suspending sales of modern rifles nationwide because of the shooting. The company also said it's removing all guns from display at its store closest to Newtown.
At the same time, the outlines of a national debate on gun control began to take shape.
A former co-chairman of the Congressional Sportsmen's Caucus, Rep. Mike Thompson, D-Calif., and 10-term House Republican Jack Kingston, a Georgia lawmaker elected with strong National Rifle Association backing, were the latest to join the call to consider gun control as part of a comprehensive, anti-violence effort next year.
"Put guns on the table. Also put video games on the table. Put mental health on the table," Kingston said.
But he added that nothing should be done immediately, saying, "There is a time for mourning and a time to sort it out. I look forward to sorting it out and getting past the grief stage."
White House spokesman Jay Carney said President Barack Obama was "actively supportive" of a plan by Sen. Dianne Feinstein, D-Calif., to introduce legislation to reinstate an assault weapons ban. While Obama has long supported a ban, he did little to get it passed during his first term.
Meanwhile, the National Rifle Association, silent since the shootings, said in a statement that it was "prepared to offer meaningful contributions to help make sure this never happens again." It gave no indication what that might entail.
Contributing to this report were Associated Press writers Allen G. Breed, Helen O'Neill, John Christoffersen and Pat Eaton-Robb in Newtown; Katie Zezima in Stratford; and Christine Armario in Miami.