The Columbine High School massacre occurred on April 20, 1999 in Columbine, Colorado. The shooting was perpetrated by two students, Eric Harris and Dylan Klebold, who killed 13 people and wounded 24 others before taking their own lives. At the time, it was one of the deadliest school shootings in United States history. The attackers carried out the massacre as an act of alleged revenge and in an attempt to gain notoriety.

Background

In April 1999, Dylan Klebold and Eric Harris attended Columbine High School in Littleton as seniors. The middle-class teenagers had been friends for several years. They worked at the same pizza parlor and shared interests in bowling, video games, and German industrial rock music. After committing a felony theft of electronics in 1998, they completed a juvenile rehabilitation program, which included anger management and community service.

Klebold, Harris, and several of their peers were known to wear black clothing and trench coats, and they often referred to themselves as the "Trench Coat Mafia". The group viewed themselves as social outsiders, and their rivalries with other student cliques at the school were widely known. Time magazine later reported that other students would harass them “to the point of throwing rocks and bottles at them from moving cars.” 
In the spring of 1998, Klebold and Harris began planning what would become one of the nation's deadliest school shootings. Their diaries and ledger documented their preparations throughout the year. In late 1998, they acquired two shotguns and a 9mm semiautomatic carbine through their eighteen-year-old friend Robyn Anderson, who purchased the weapons legally at a gun show.

Their planning intensified in early 1999. On January 23, they met Mark Manes, a twenty-two-year-old former Columbine student, at another gun show. Manes sold them a TEC-DC9 semiautomatic handgun for $500. Their final preparations occurred on April 19, 1999, when Manes sold Harris 100 rounds of 9mm ammunition for twenty-five dollars.
The attackers planned to detonate a homemade propane bomb at Columbine High School when the cafeteria and library would be most populated. They marked April 20, 1999, as the date to "rock and roll" in their ledger, planning to end the attack by taking their own lives.

The Attack

Initial Attack

On Tuesday, April 20, 1999, the school day was in progress at Columbine High School. During the fifth period, most students were in class, while others had gathered in the cafeteria as the lunch hour approached. The attackers began by opening fire on two students eating outside, before moving inside and beginning to shoot at other students near the entrance and near the cafeteria. They also began to throw pipe bombs.

Upon hearing the initial commotion many Columbine students laughed, assuming it was just the annual senior prank or an accident in the science labs. As it became clear to more people in the school that the attack was real and not a prank, panic began to spread. Many who were able to fled from the school into the surrounding area, while others were forced to remain in the building and seek shelter. Students and staff hid in closets, offices, and classrooms, calling parents and police on cell phones. In the science wing, teachers unscrewed the light bulbs and armed themselves with fire extinguishers and X-Acto knives, hoping that the attackers would not discover their position. 

Senior Zak Cartaya and several others hid out in the choir room office after hearing shots and seeing a “large fireball” in the hallway. Cartaya later said that “we used this big old filing cabinet to cover the door, then we got under Mr. Andre’s desk. Just when we got through with the barricade, the shooters opened fire into the choir room to make sure nobody was hiding. We couldn’t talk; we were afraid that they would hear us. You could hear one of the gunman outside. You could hear shots everywhere… We were telling people to shut up and be quiet. We couldn’t let people cry.”

Junior Brea Pasquale recalled that “you could hear them laughing as they ran down the hallways shooting people.” One of the Columbine shooters pointed a gun at Pasquale, but ultimately did not harm her, claiming, “I’m doing this because people made fun of me last year”. Fire alarms blared and sprinklers drenched entire sections of the school. In the greenhouse of the science wing, students and teachers heard one of the gunmen shout out, “Today I am going to die!” 

Business teacher and coach William David Sanders had been present in the cafeteria during the beginning of the attack. Having recognized the sound of gunshots, he began moving through the school to warn students to flee. Sixteen-year-old Lexis Coffey-Berg looked up from a biology exam to see Sanders shot twice in the back as he ran into a classroom to warn the students. Sanders fell onto a desk, bleeding profusely. An instructor phoned paramedics as students attempted to administer first aid and made bandages from their clothing. With paramedics talking them through Sanders’s care, the students held a sign to the window reading, “HELP, BLEEDING TO DEATH.”

The Library

Witnesses later described the unfolding events through firsthand accounts. A boy who had been struck in the leg hurled an explosive away from a crowd of his wounded classmates. Another lay on top of his sister and her friend in a desperate attempt to shield them from the gunfire. 

When Nielson and Anderson reached the library, they found it already crowded with panicked students. As the students began hiding under tables in the library, the two gunmen burst in, shouting, “Who’s next? Who’s ready to die? We’ve waited to do this a long time. All the jocks stand up, we are going to kill every one of you!” More shots rang out as students pleaded for their lives. The shooters reportedly called one student, Isaiah Shoels, a racial slur before shooting him dead, along with his fellow football teammate, Matthew Kechter. One of the gunmen spotted a girl crouching beneath a desk, and muttered “Peekaboo” before shooting her.

At 11:36, Klebold and Harris left the library, having killed ten and injured twelve others. They wandered through the school without taking any more lives, and briefly returned to the cafeteria to attempt to set off the bombs they had planted. After failing, they returned to the library and found it evacuated. By 12:08, both attackers took their own lives using their firearms.

Response from Authorities

Within minutes of the first shots fired, hundreds of police officers, paramedics, firefighters, and news media gathered outside, taking shelter behind their vehicles. 
The attack was breaking news across the country, and aired live by many major news stations. Millions of Americans watched on television as police, SWAT teams, FBI and ATF agents, and reporters descended on the scene along with ambulances, police vehicles, helicopters, and even a military armored personnel carrier. Amid speculation of hostage-taking and an unknown number of gunmen and bombers, reporters interviewed panicked and exhausted students who had fled the scene. Students recognized the gunmen as their classmates. Reports confirmed multiple casualties, with the highest concentration of victims in the library.

Starting around noon, ambulances took the wounded to area hospitals. For several hours, officials led streams of students out of the building, ordering them to keep their hands on their heads as they ran single-file to awaiting buses. Before boarding, each student was frisked—a precaution to identify gunmen or accomplices attempting to sneak away from the carnage. The buses transported the students to nearby schools that had been immediately evacuated upon news of the shootings, where they were identified and reunited with their families. In the science room, the business teacher, Dave Sanders, remained conscious for over four hours as he was attended to by a group of students. He died moments after paramedics arrived.

End of Day

By the day’s end, lingering fears of booby traps and undetonated bombs led to thorough sweeps of the building but prevented a complete count or removal of the bodies. Initial estimates of up to twenty-five fatalities stunned the millions following the situation on television and the radio. Authorities later clarified that the exact figure was fifteen deaths—including the two attackers. Twelve bodies were found in the library. 

The thirteen victims who lost their lives were: Cassie Bernall, 17; Steven Robert Curnow, 14; Corey DePooter, 17; Kelly Fleming, 16; Matthew Kechter, 16; Daniel Mauser, 15; Daniel Rohrbough, 15; William David Sanders, 47; Rachel Scott, 17; Isaiah Shoels, 18; John Tomlin, 16; Lauren Townsend, 18; and Kyle Velasquez, 16.

In the hours following the massacre, police defused more than thirty propane tank bombs and pipe bombs throughout the campus, including some found in the attackers’ cars in the school parking lot. All told, the killers fired more than 900 rounds of ammunition during the forty-five-minute attack. In addition to the fifteen fatalities, twenty-three students were wounded, many of them critically. Though a few of the injured were wounded in bomb blasts, all of the fatalities stemmed from gunshot wounds.

Aftermath

The violence at Columbine sparked worldwide discussions about school security. U.S. Secretary of Education Richard W. Riley called for a "public outcry," citing concerns about gun access and violence in American culture. He urged parents to “reach out to your children and listen to them. We have to do everything we can to connect even to the most angry and alienated young person.” In Denver and around the country, massive fundraising efforts get under way to aid hospitalized students and victims’ families. 
Media coverage focused intensely on the “Trench Coat Mafia,” a clique of students which included Harris and Klebold, , leading to increased scrutiny of Goth subculture. Musician Marilyn Manson canceled his Denver concert and expressed sympathy for the community while arguing against attributing blame to Goth subculture. Television networks adjusted their programming in response to the tragedy. Denver's professional sports teams commemorated the victims by wearing Columbine High School patches and black armbands.

On April 25, 1999, 70,000 people attended a public memorial service in a theater parking lot. Vice President Al Gore addressed the crowd, fighter planes flew overhead, and Columbine students Jonathan and Stephen Cohen performed a tribute song. Attendees wore Columbine's silver and blue ribbons, which became a statewide symbol of remembrance. At Clement Park, adjacent to the school, an impromptu memorial grew to fifty feet wide and a quarter mile long with flowers, crosses, letters, and other items. Many of these items are now in the collection of History Colorado, the state historical society. 

Jefferson County schools implemented new safety protocols, including bomb sweeps, emergency procedure reviews, and on-site crisis teams. Columbine students resumed classes at Chatfield High on May 3. After $1.2 million in renovations, Columbine High School reopened on August 16, 1999.

The total cost of the tragedy reached nearly $6 million, including $4.4 million in state funds for law enforcement, mental health, and school expenses. Several parents, including the Klebolds, filed intent to sue the school and police for negligence, claiming authorities missed early warning signs.

Legacy

The Columbine Memorial Committee formed in June 1999. This committee had the difficult decision of how to memorialize such a significant tragedy. Decisions on what would remain the same and what would be removed were a constant source of contention between students, parents, and community members. Jeff Garkow, a Columbine student from 2002 to 2006, recalls that, “There were conversations right after the shooting. Like, should Columbine be demolished?” Some argued that removing the library would help the school distance itself from the tragedy and discourage unwanted attention, as trespassing had become a problem on the campus. This idea did not sit well with others as they thought that removing the library would erase the memory of what happened completely. After extensive discussions among community members, school staff, parents, and students, a decision was made to demolish the library where most victims died. The Hope Columbine Memorial Library replaced it, featuring a large gray stone inscribed with the thirteen victims' names.

Clement Park houses the public memorial, which consists of two main elements: the Ring of Remembrance, honoring the thirteen victims, and the Wall of Healing, displaying anonymous quotes from survivors to preserve their experiences.

The community also established an annual Day of Service, during which students, staff, alumni, and community members participate in volunteer projects.