Here's a look at some of those who died in the attack:
•Dawn Lafferty Hochsprung was the 47-year-old principal of Sandy Hook Elementary School, a wife and mother of two daughters and three stepdaughters. Among her accomplishments was overseeing the installation of a new security system at the school.
•Mary Sherlach was the 56-year-old school psychologist, wife and mother of two daughters in their late 20s. She was shot to death in a hall way while investigating the sound of the gunshots.
•Lauren Rousseau was a 30-year-old permanent substitute teacher. She dreamed of being a teacher before she even entered kindergarten.
•Victoria Soto was a 27-year-old first grade teacher, who died while protecting her students from the shooter.
•Olivia Engel was a six-year-old girl whose family called "a precocious and completely endearing" child.
•Emilie Parker was a six-year-old girl and "the type of person who could light up a room," her father said.
 
Other victims include:

Rachel Davino, 29; Anne Marie Murphy, 25; Charlotte Bacon, 6; Daniel Barden, 7; Josephine Gay, 7; Ana Marquez-Greene, 6; Dylan Hockley, 6; Madeleine Hsu, 6; Catherine Hubbard, 6; Chase Kowalski, 7; Jesse Lewis, 6; James Mattioli, 6; Grace McDonnell, 7; Anne Marie Murphy, 52; Jack Pinto, 6; Noah Pozner, 6; Caroline Previdi, 6; Jessica Rekos, 6; Avielle Richman, 6; Benjamin Wheeler, 6; Allison Wyatt, 6.

Source: CNN