Many athletes took to social media websites to process what happened, discussing their shock and horror, and openly worrying about their kids at school.
"Innocent victims just gone," Miami Heat star LeBron James said in a series of posts on Twitter. "This is really messing with my mind. Kids is everything to me! And of course i have 2 of my own in elementary school as well. I can't imagine it happening to my kids school. I and the rest of the families would be devastated! Something has to be done."
Golfer John Daly talked about home schooling his children, and outspoken Minnesota Vikings punter Chris Kluwe wondered about the road ahead.
"The way we deal with this tragedy in CT will tell us a lot about where we're headed as a society. Do we only address the symptoms (i.e. just gun control laws)? Or do we also address the disease — how we treat each other and those who need help," Kluwe said in a couple of posts on Twitter.
There also was some anger.
Montreal Canadiens captain Brian Gionta tweeted: "Not sure if there is anything lower than harming innocent children." He ended the tweet with a hashtag of "coward," then was critical of the media interviewing young children outside the school.
"At some point, we've got to get past bureaucracy and all the nonsense and do something about this so our kids can be safe," said New Orleans Hornets coach Monty Williams, who has five children ranging in age from 2 to 14.
"If we can go to outer space and take care of trees and rivers and animals, we can do a better job of taking care of our kids. It's just a sad situation."