When a gunman killed 20 first graders and six adults with an assault rifle at Sandy Hook Elementary School in 2012, it rattled Newtown, Conn., and reverberated across the world. Since then, there have been at least 239 school shootings nationwide. In those episodes, 438 people were shot, 138 of whom were killed.

The data used here is from the Gun Violence Archive, a nonprofit that began tracking school shootings in 2014, about a year after Sandy Hook.

Gunshot Victims in School Shootings

Killed

Injured

Sandy Hook

Jan. 2014

Feb. 2014

March 2014

April 2014

May 2014

June 2014

July 2014

Aug. 2014

Sept. 2014

Oct. 2014

Nov. 2014

Dec. 2014

Jan. 2015

Feb. 2015

March 2015

April 2015

May 2015

June 2015

July 2015

Aug. 2015

Sept. 2015

Oct. 2015

Nov. 2015

Dec. 2015

March 2016

April 2016

May 2016

June 2016

July 2016

Aug. 2016

Sept. 2016

Oct. 2016

Nov. 2016

Dec. 2016

Jan. 2016

Feb. 2016

Feb. 2017

May 2017

June 2017

July 2017

Aug. 2017

Sept. 2017

Oct. 2017

Nov. 2017

Dec. 2017

Jan. 2017

March 2017

April 2017

Jan. 2018

Feb. 2018

Parkland, Fla.

Gunshot Victims in School Shootings

Killed

Injured

Sandy Hook

Jan. 2014

Feb. 2014

March 2014

Apr. 2014

May 2014

June 2014

July 2014

Aug. 2014

Sept. 2014

Oct. 2014

Nov. 2014

Dec. 2014

Jan. 2015

Feb. 2015

March 2015

Apr. 2015

May 2015

June 2015

July 2015

Aug. 2015

Sept. 2015

Oct. 2015

Nov. 2015

Dec. 2015

March 2016

Apr. 2016

May 2016

June 2016

July 2016

Aug. 2016

Sept. 2016

Oct. 2016

Nov. 2016

Dec. 2016

Jan. 2016

Feb. 2016

Feb. 2017

May 2017

June 2017

July 2017

Aug. 2017

Sept. 2017

Oct. 2017

Nov. 2017

Dec. 2017

Jan. 2017

March 2017

Apr. 2017

Jan. 2018

Feb. 2018

Parkland, Fla.

Gunshot Victims in School Shootings

Killed

Injured

Sandy Hook

July

Aug.

Jan. 2014

Feb.

March

April

May

June

Sept.

Oct.

Nov.

Dec.

Jan. 2015

Feb.

March

April

May

June

July

Aug.

Sept.

Oct.

Nov.

Dec.

March

April

May

June

July

Aug.

Sept.

Oct.

Nov.

Dec.

Jan. 2016

Feb.

Feb.

March

April

May

June

July

Aug.

Sept.

Oct.

Nov.

Dec.

Jan. 2017

Feb.

Jan. 2018

Parkland, Fla.

Gunshot Victims in School Shootings

Killed

Injured

Sandy Hook

Jan. 2014

Feb.

March

April

May

June

July 2014

Aug.

Sept.

Oct.

Nov.

Dec.

Feb.

March

April

May

June

Jan. 2015

July 2015

Aug.

Sept.

Oct.

Nov.

Dec.

Jan. 2016

March

Feb.

April

May

June

July 2016

Aug.

Sept.

Oct.

Nov.

Dec.

Jan. 2017

March

April

May

June

Feb.

July 2017

Aug.

Sept.

Oct.

Nov.

Dec.

Feb.

Feb.

Feb.

Feb.

Feb.

Jan. 2018

Gunshot Victims in School Shootings

Killed

Injured

Sandy Hook

Jan. ’14

Feb.

March

April

May

June

July ’14

Aug.

Sept.

Oct.

Nov.

Dec.

Jan. ’15

Feb.

March

April

May

June

July ’15

Aug.

Sept.

Oct.

Nov.

Dec.

March

April

May

June

Jan. ’16

Feb.

July ’16

Aug.

Sept.

Oct.

Nov.

Dec.

Jan. ’17

Feb.

March

April

May

June

July ’17

Aug.

Sept.

Oct.

Nov.

Dec.

Feb.

Jan. ’18

Parkland, Fla.

Source: Gun Violence Archive
Note: Shootings in 2013 are not included because complete data was not available in that year. Months with blanks indicate no shootings archived.

The shootings have taken place at sporting events and in parking lots, cafeterias, hallways and classrooms.

A shooting took place Wednesday at Marjory Stoneman Douglas High School in Parkland, Fla., about an hour northwest of Miami. As of Wednesday night, 17 people had been killed and the number of people injured was unknown.

Sixteen of the 239 shootings shown below can be classified as mass shootings, events in which four or more people are shot.

On average, there have been about five school shootings each month, including episodes that were not mass shootings.

15 school shootings

10

5

Jan. 2014

Jan. 2015

Jan. 2016

Jan. 2017

Jan. 2018

15 school shootings

10

5

2014

2015

2016

2017

2018

15 school shootings

10

5

2014

2015

2016

2017

2018

Source: Gun Violence Archive.

Each of the episodes falls under the definition of “school shooting” used by the Gun Violence Archive.

The nonprofit defines a school shooting as an episode on the property of an elementary school, secondary school or college campus. Another defining characteristic is timing — shootings must occur during school hours or during extracurricular activities.

Only episodes in which people were injured or killed by gunfire are included. Injuries like a leg broken while fleeing the site were not archived.

Police reports often leave out the origin of guns used in school shootings, but researchers say a significant portion of the guns used in such episodes come from the shooters’ homes.

Many children have access to unlocked guns at home. Data from gun ownership surveys conducted by the Pew Research Center show that 54 percent of gun owners with children under 18 living at home say they keep all of their guns locked away.

Fourteen states and Washington, D.C., have laws that impose criminal liability on those who store guns at home and know “or reasonably should know” that those firearms are accessible to children.

In a study conducted in 2000 by the RAND Corporation, researchers estimated that more than 22 million children live in homes with a firearm.

Correction: Feb. 15, 2018

An earlier version of this article misstated the number of school shootings since 2012. It was 239, not 273. The number of people shot was also misstated. It was 438, not 439.