Some parents said they struggled with mixed emotions after their own children survived the massacre that took so many young lives.
After receiving word of the shooting, Tracy Hoekenga said she was paralyzed with fear for her two boys, fourth-grader C.J. and second-grader Matthew.
"I couldn't breathe. It's indescribable. For a half an hour, 45 minutes, I had no idea if my kids were OK," she said.
Matthew said a teacher ordered him and other students to their cubbies, and a police officer came and told them to line up and close their eyes.
"They said there could be bad stuff. So we closed our eyes and we went out. When we opened our eyes, we saw a lot of broken glass and blood on the ground," he said.
David Connors, whose triplets attend the school, said his children were told to hide in a closet during the lockdown.
"My son said he did hear some gunshots, as many as 10," he said. "The questions are starting to come out: 'Are we safe? Is the bad guy gone?'"
At the vigil, Newtown High School freshman Claudia Morris, 14, said students had gathered in the school hallways after the massacre, asking each other, "Are you all right? Are you all right?"
"No one has answers to why this happened," she said. "It just seems so unreal."
Associated Press writers John Christoffersen and Adam Geller contributed to this report.