CNN — Here's a look at what you need to know about the Sandy Hook Elementary School shootings in Newtown, Connecticut.
December 14, 2012 - Twenty children and six adults are killed at the school by 20-year-old Adam Lanza, who had earlier killed his mother, Nancy Lanza, in their Sandy Hook home.
As police approached the school, Lanza took his own life.
It is the second-deadliest shooting in US history.
Other Facts: Weapons found at the scene were legally purchased by Nancy Lanza.
Lanza used a Bushmaster AR-15 during the shooting spree. Three weapons were found next to his body; the semiautomatic .223-caliber rifle made by Bushmaster, and two handguns. A shotgun was found in his car.
The Shooter: Birth name: Adam Lanza
Birth date: April 22, 1992
Birth place: Kingston, New Hampshire
Father: Peter Lanza
Mother: Nancy (Champion) Lanza
Sibling: Ryan Lanza, brother
Lanza's parents were divorced in September 2009.
Lanza reportedly had Asperger's syndrome.
Timeline: December 14, 2012: At an unknown time, 20-year-old Adam Lanza kills his mother Nancy, 52. Lanza then drives his mother's car to Sandy Hook Elementary, about five miles away.
At approximately 9:30am, Adam Lanza arrives at Sandy Hook Elementary, a school with about 700 students. The principal, Dawn Hochsprung, had installed a new security system that required every visitor to ring the front entrance's doorbell for admittance. Lanza shoots his way through the entrance.
Principal Hochsprung, school psychologist Mary Sherlach and Vice Principal Natalie Hammond step out to the hall to see what is going on. Hochsprung and Sherlach are killed, and Hammond is injured.
The first 911 calls to police are made at approximately 9:30. Police and first responders arrived approximately five minutes later.
Lanza enters the classroom of substitute teacher Lauren Rousseau. Lanza kills 14 children as well as Rousseau and a teacher's aide.
He then enters the classroom of teacher Victoria Soto. Six children in the room, as well as Soto and a teacher's aide, are killed. Lanza kills himself in the same classroom.
At about 3:15pm, an emotional President Barack Obama gives a televised address, "We're going to have to come together and take meaningful action to prevent more tragedies like this, regardless of the politics." He orders flags to be flown at half-staff at the White House and other federal buildings.
December 15, 2012 - Connecticut State Police release the names of the victims: six adult women, 12 girls ages six and seven, and eight boys, also ages six and seven.
December 16, 2012 - President Barack Obama visits with the relatives of those who were killed. He also attends an interfaith vigil and says, "We can't tolerate this anymore. These tragedies must end, and to end them we must change."
December 17, 2012 - Connecticut Governor Dan Malloy announces a statewide moment of silence on Friday, December 21. He also requests that bells be tolled 26 times in memory of the victims.
December 18, 2012 - Newtown Superintendent of Schools Janet Robinson announces that Sandy Hook students will remain out of school until January. At that time, they will be taught in a converted middle school.
January 8, 2013 - Governor Malloy announces the names of the people who will serve on the Sandy Hook Advisory Commission, a panel that will review current policy and make recommendations on public safety, mental health, and violence prevention policies.
March 2013 - A new police report reveals that Adam Lanza possessed a list of 500 of the world's most notorious mass murderers, and was trying to rack up the greatest number of kills in history.
The Victims at Sandy Hook school: Allison Wyatt, 6 Ana Marquez-Greene, 6 Anne Marie Murphy, 52 (Teacher) Avielle Richman, 6 Benjamin Wheeler, 6 Caroline Previdi, 6 Catherine Hubbard, 6 Charlotte Bacon, 6 Chase Kowalski, 7 Daniel Barden, 7 Dawn Lafferty Hochsprung, 47 (Principal) Dylan Hockley, 6 Emilie Parker, 6 Grace McDonnell, 7 Jack Pinto, 6 James Mattiloi, 6 Jesse Lewis, 6 Jessica Rekos, 6 Josephine Gay, 7 Lauren Rousseau, 30 (Teacher) Madeleine Hsu, 6 Mary Sherlach, 56 (Psychologist) Noah Pozner, 6 Olivia Engel, 6 Rachel D'Avino, 29, (Therapist) Victoria Soto, 27 (Teacher)