The images of teenagers running from their school with their hands up – as seen on April 20, 1999, at Columbine High School -- has become a hauntingly familiar sight at subsequent school shootings.
And for many, including eventual school shooters, there was something about the Columbine shooting that drew their interest.
John Cohen, a former Department of Homeland Security official who led efforts to combat mass shootings, said that Columbine “absolutely” influenced subsequent shootings.
“As law enforcement has studied the individuals who have committed school shootings and other mass casualty attacks, one of the common characteristics they’ve observed is these individuals tend to study past mass shootings,” said Cohen, who is now an ABC News contributor.
“As it relates specifically to school shootings, we find that columbine seems to be the one incident hat school shooters look at. It seems to resonate with individuals that have the behavioral characteristics consistent with this type of attacker,” he said.
“The people who conduct school shootings tend to be disaffected mentally unwell individuals searching for a sense of social connection and life meaning. They go online, they look at past attacks and in a perverse way, they connect with not only past incidents but also past attackers,” Cohen said, adding that “the story of the Columbine shooters is a story that resonates with a group of kids that are experiencing similar situations.”
While there are hundreds of shootings that have taken place at schools across the U.S. in the past 20 years, leaving broken homes and broken childhoods in their wake, there have been 11 which can be classified as mass shootings. The FBI defines a mass shooting as an incident in which four or more victims, not including the suspect, are killed.
1. Virginia Tech – April 16, 2007 – 32 victims
The deadliest school shooting in U.S. history took place on the campus of Virginia Polytechnic Institute and State University, commonly known as Virginia Tech, in Blacksburg.
At the time of the shooting, the 32 shooting victims made it the deadliest shooting incident in U.S., though that grisly title would later be overtaken by the shootings at Pulse nightclub in 2016 and later the shooting at a country music festival in Las Vegas in 2017.
The shooting took place almost exactly eight years after the Columbine shooting, when a 23-year-old student opened fire at two locations on campus – first in a dorm room and then in an academic building across campus.
In total, he killed 32 victims and injured 23 others before turning the gun on himself.
2. Sandy Hook Elementary School – Dec. 14, 2012 – 26 victims
A half a decade later, another young man devastated a community when, after first killing his mother, he drove to a nearby elementary school and opened fire, killing 20 children and six school administrators before killing himself.
The shooting at Sandy Hook Elementary School in the sleepy town of Newtown, Connecticut, prompted a national outpouring of grief. Emotions ran high when then-President Barack Obama made a statement about the shooting, pausing at one point to wipe away a tear.
“The majority of those who died today were children -- beautiful little kids between the ages of 5 and 10 years old," he said in the White House briefing room. "They had their entire lives ahead of them -- birthdays, graduations, weddings, kids of their own. Among the fallen were also teachers -- men and women who devoted their lives to helping our children fulfill their dreams. So our hearts are broken today.”
The outrage over the shooting led to a push for federal changes to gun laws, but the bill did not pass. Instead, in the years since the Sandy Hook shooting, a number of states have changed their local laws.
3. Marjory Stoneman Douglas High School – Feb. 14, 2018 – 17 victims
While the response of “thoughts and prayers” offered after mass shootings was once again decried by many as inadequate, the reaction after the shooting at Marjory Stoneman Douglas High School differed from others.
Almost immediately after the shooting, the teens who survived stepped into action, launching what would be a national push for gun control, culminating in the March For Our Lives.
New gun laws were passed in Florida a little over three weeks after the shooting, when 14 high school students and three school administrators were killed.
4. Santa Fe High School – May 18, 2018 – 10 victims
Just three months after the Parkland shooting, another high school was the scene of a mass shooting, this time in Texas.
In total, eight students and two teachers were killed by a 17-year-old gunman. Texas Gov. Greg Abbott said that the shooter allegedly wrote in journals that he wanted to carry out the shooting and then commit suicide, but on the day of the shooting, he gave himself up to authorities.
5. Umpqua Community College – Oct. 1, 2015 – 9 victims
A student in one of the writing classes offered at the Roseburg, Oregon, school started shooting victims, reportedly one-by-one.
The 26-year-old shooter fatally shot himself at the scene.
“Our thoughts and prayers are not enough,” then-President Obama said on the day of the shooting. "It's not enough. It does not capture the heartache and grief and anger that we should feel and it does nothing to prevent this carnage from being inflicted in someplace else in America."
6. Red Lake Senior High School – March 21, 2005 – 7 victims at the school
The deadly shooting spree on Red Lake Indian Reservation in Minnesota, started before it unfolded at the local high school.
First the 16-year-old shooter killed his grandfather and the grandfather's girlfriend before driving to Red Lake Senior High School, which he used to attend, and opening fire.
The shooter killed seven people at the school, including students, a teacher and a security guard, and injured five others. The shooter was injured by responding officers but then reportedly retreated and fatally shot himself.
7. Oikos University – April 2, 2012 – 7 victims
A Korean Christian college was the site of a deadly shooting in 2013, when a 43-year-old former student returned to the campus of Oikos University and opened fire.
There were seven victims killed and three others injured before the shooter was taken into custody. The suspect reportedly went looking for a female administrator that he was angry with, but when he realized she wasn’t there, he asked students to line up.
When they didn’t comply, he started shooting.
At the time of this shooting, which happened in Oakland, California, it was the fourth-deadliest shooting on an American college campus.
8. West Nickel Mines School – Oct. 2, 2006 – 5 victims
A 32-year-old local milk delivery man drove a pickup truck to the one-room Amish schoolhouse after dropping off his own children at their school bus.
The shooter, who was not Amish, had a handgun in his hand when he entered the school. A police officer later said that it appears that the suspect went to the school with the intention of killing young girls, after he purposefully let the young boys and adults out of the schoolhouse.
A police official said that the girls were lined up against the chalkboard and "he had taken wire and bound their legs together." The suspect's wife found notes that the suspect had left for their children, and thinking that something was wrong, she called his cell phone.
"He made some statement about revenge for something in his life 20 years ago," the police official told ABC News at the time.
The shooter called 911 and gave a warning before he started shooting, eventually killing five girls and injuring three others. The suspect also fatally shot himself.
9. Northern Illinois University – Feb. 14, 2008 – 5 victims
A former graduate student who opened fire after walking into an auditorium during an oceanography class reportedly left a Valentine's Day note for his girlfriend before leaving for the shooting.
The shooting at Northern Illinois University, where five people were killed and at least 16 others were injured, was reportedly influenced by Columbine -- as the 27-year-old suspect "examined the methods" of the Colorado shooting and was "fascinated" by Columbine, according to a police report on the case.
The shooting took place a decade to the day before the deadly shooting at Marjory Stoneman Douglas High School in Parkland, Florida.
10. Santa Monica College – June 7, 2013 – 5 victims
While the shooting at Santa Monica College would not be considered a mass deadly shooting itself since there were three people killed there and not four, there were two others that the shooter at the school killed before arriving on the scene.
The suspect reportedly fatally shot his father and brother, set their house on fire, and then made his way towards the college campus.
Police said the suspect was wearing a protective vest and carrying so much weaponry he was, in the words of one official, "ready for battle."
11. Marysville Pilchuck High School – Oct. 24, 2014 – 4 victims
The 15-year-old shooter who fatally shot four students before killing himself reportedly lured his victims to his lunch table via text before the shooting.
"The only pre-planning of the event that detectives are able to confirm is that [the shooter] had arranged for a meeting of friends during lunch in the cafeteria. A witness confirms that the five victims were seated at the table when the shooter opened fire, striking the victims before turning the gun on himself," police said in a statement after the Marysville Pilchuck High School shooting.
Not all of the victims died on the scene, but some died later in the hospital, changing the death counts in the immediate aftermath.