On April 20, 1999, high school senior students Eric Harris and Dylan Klebold shot and killed 13 students and one teacher in a school shooting and attempted bombing at Columbine High School in Columbine, Colorado, United States. Twenty people were injured by the gunfire, and three others were injured while trying to escape. The attack ended when Harris and Klebold committed suicide. The Columbine massacre was the deadliest mass shooting at a K–12 school in U.S. history until the Sandy Hook Elementary School shooting in December 2012. It was also the deadliest high school shooting until Parkland high school in 2018. Columbine is considered among the most infamous massacres in the United States, which as of June 2025, had inspired more than 70 copycat crimes, a phenomenon dubbed the Columbine effect, and Columbine has become a byword for modern school shootings.
Harris and Klebold, who planned for roughly a year, intended the attack to be primarily a bombing and only secondarily a shooting. The pair launched a shooting attack after the homemade bombs they planted in the school failed to detonate. Their motive remains uncertain. The police were slow to enter the school and were strongly criticized for not intervening during the shooting. The incident resulted in the introduction of the immediate action rapid deployment (IARD) tactic, which is used in active-shooter situations, and an increased emphasis on school security with zero-tolerance policies. The violence sparked debates over American gun culture and gun control laws, high school cliques, subcultures (e.g. goths), outcasts, and school bullying, as well as teenage use of pharmaceutical antidepressants, the Internet, and violence in video games and film.
Many makeshift memorials were created after the massacre, including ones using victim Rachel Scott's car and John Tomlin's truck. Fifteen crosses for the victims and the shooters were erected on top of a hill in Clement Park. Many people objected to the inclusion of crosses for the perpetrators and these were later removed from the site. Planning for a permanent memorial began in June 1999. The resulting Columbine Memorial opened to the public in September 2007.
Perpetrators
Eric Harris
Eric David Harris (April 9, 1981 – April 20, 1999) was born in Wichita, Kansas. The Harris family relocated often, as Harris's father was a US Air Force transport pilot. The family moved from Plattsburgh, New York, to Littleton, Colorado, in July 1993, when his father retired from military service. Harris attended Ken Caryl Middle School, where he met Klebold. In 1996, the Harris family purchased a house south of Columbine High School (CHS). Harris's older brother attended college at the University of Colorado Boulder.
Dylan Klebold
Dylan Bennet Klebold ( KLEE-bohld; September 11, 1981 – April 20, 1999) was born in Lakewood, Colorado. His parents were pacifists and attended a Lutheran church with their children. Both Dylan and his older brother attended confirmation classes in accordance with the Lutheran tradition. Klebold was named after poet Dylan Thomas. Klebold attended Normandy Elementary for first and second grade before transferring to Governor's Ranch Elementary, and became part of the Challenging High Intellectual Potential Students (CHIPS) program.
Background
Criminal history
In 1996, 15-year-old Harris created a private website on America Online (AOL), initially to host video game levels (known as WADs) that he created for the first-person shooter games Doom, Doom II, and Quake. On the site, Harris began a blog, which included details of mischief and vandalism, such as lighting fireworks with Klebold and others. Harris referred to these acts as "rebel missions" and the blog posts as "mission logs". In early 1997, after classmate Brooks Brown had told Harris's parents where he hid alcohol, to get back at Harris after he had previously thrown a chunk of ice at Brown's car windshield, the blog posts showed signs of Harris's anger against society. By the end of the year, the site contained instructions on how to make explosives (specifically pipe bombs). In August 1997, Harris wrote on the blog "All I want to do is kill and injure as many of you as I can, especially a few people. Like Brooks Brown." After Brown's parents viewed the site, they contacted the Jefferson County Sheriff's Office on August 7, 1997. An investigator drafted an affidavit requesting a search warrant for the Harris household, but it was never submitted to a judge.
On January 30, 1998, Harris and Klebold were arrested for breaking into a white van parked near Littleton and stealing tools and computer equipment. The judge sentenced them to a 12-month juvenile diversion program. As a result, they both attended mandatory classes such as anger management and met with diversion officers. They were both released from the program a month early.
Writings
Shortly after the court hearing for the van break-in, Harris reverted his website back to only hosting user-created levels of Doom and began keeping a journal. Klebold had already been keeping a personal journal since March 1997. In both their journals, Harris and Klebold later plotted the attack. Harris's plan for an attack included possibly escaping to a foreign country or hijacking an aircraft at the Denver International Airport and crashing it into a building in New York City.
Klebold and Harris both made entries in their journals on topics related to sexuality. Klebold expressed shame for his sexual interests, which included bondage and foot fetishism, stating that, "My humanity has a foot fetish, & bondage exteme [sic] liking. I try to thwart it..." Harris described his desire for raping and torturing women in his bedroom, and also expressed interest in cannibalism, stating that he would like to dismember a woman with whom he could have "animalistic sex" and eat her flesh.
Harris and Klebold's schoolwork displayed themes of violence. In December 1997, Harris wrote a paper on school shootings titled "Guns in School", and a poem from the perspective of a bullet. Klebold wrote a short story about a man killing students which worried his teacher so much that she alerted his parents; when Klebold was confronted about it, he said it was "just a story". For one project, Harris wrote a paper on Nazi Germany and Klebold wrote a paper on Charles Manson. In a psychology class, Harris wrote that he dreamed of going on a shooting spree with Klebold, with Harris's journals describing several experimental bomb detonations.
Nearly a year before the massacre, Klebold wrote a message in Harris's 1998 yearbook: "killing enemies, blowing up stuff, killing cops!! My wrath for January's incident will be godlike. Not to mention our revenge in the commons"; "the commons" was slang for the school cafeteria.
Tapes
Harris and Klebold were both enrolled in video-production classes and kept five video tapes that were recorded with school video equipment. Only two of these, Hitmen for Hire and Rampart Range, and part of a third known as Radioactive Clothing, have been released. The remaining three tapes detailed their plans and reasons for the massacre, including the ways they hid their weapons and deceived their parents. Most were filmed in the Harris family basement, and are thus known as the basement tapes. Thirty minutes before the attack, they made a final video saying goodbye and apologizing to their friends and families.
In December 1999, before anyone besides investigators had seen them, Time magazine published an article on these tapes. Select victim families and journalists were allowed to view them, though the tapes were then withheld from the public, and later destroyed in 2011, out of fear of inspiring future massacres. Transcripts of some of the dialogue and a short clip recorded surreptitiously by a victim's father still exist, with the transcripts being online via various resources. The pair claimed they were going to make copies of the tapes to send to news stations but never did so.
When an economics class had Harris make an ad for a business, he and Klebold made a video called Hitmen for Hire on December 8, 1998, which was released in February 2004. It depicts them as part of the Trench Coat Mafia, a clique in the school who wore black trench coats and opposed jocks, extorting money for protecting preps from bullies. Klebold and Harris themselves were apparently not a part of the Trench Coat Mafia but were friends with some of its members and wore trench coats on the day of the massacre. Hitmen for Hire showed them walking the halls of the school, and shooting bullies outside with fake guns. A video was released showing them doing target practice in nearby foothills known as Rampart Range, with the weapons they later used in the massacre.
Harris left a micro cassette labeled Nixon on the kitchen table. On it, Harris said "It is less than nine hours now," placing the recording at some time around 2:30 am. He went on to say "People will die because of me," and "It will be a day that will be remembered forever."
Weaponry
Guns
In the months prior to the attacks, Harris and Klebold acquired two 9mm firearms and two 12-gauge shotguns. Harris had a Hi-Point 995 carbine with thirteen 10-round magazines and a Savage-Springfield 67H pump shotgun. Klebold used a 9mm Intratec TEC-DC9 semi-automatic handgun with one 50-, one 24-, and two 36-round magazines and a Stevens 311D double-barreled shotgun. Harris's shotgun was sawed-off to around 26 inches (66 cm) and Klebold shortened his shotgun's length to 23 inches (58 cm), a felony under the National Firearms Act.
On November 22, 1998, their friend Robyn Anderson purchased a carbine rifle and the two shotguns for the pair at the Tanner Gun show, as they were too young to legally purchase the guns themselves. After the attack, she told investigators that she had believed the pair wanted the weapons for target shooting and denied that she had prior knowledge of their plans. Anderson was not charged.
Harris and Klebold both held part-time jobs at a local Blackjack Pizza. Through Philip Duran, one of their coworkers, Klebold bought a TEC-9 handgun from Mark Manes for $500 ($966.00 in ) at another gun show on January 23. Manes and Duran were both prosecuted after the massacre. Each was charged with supplying a handgun to a minor and possession of a sawed-off shotgun. After both pled guilty, Manes and Duran were sentenced to a total of six years and four-and-a-half years, respectively, in prison.
Explosives
In addition to the firearms, the complex and highly planned attack involved several improvised explosive devices. Harris and Klebold constructed a total of 99 bombs. These included 27 pipe bombs, 48 carbon-dioxide cartridges filled with gunpowder (called "crickets"), seven Molotov cocktails, and 15 propane tanks converted to bombs, five of which were 20-pounds (nine kg) or more. Two propane bombs were used in the cafeteria, two in the shooters' cars, and in another location intended as a diversion. For ignition, they used storm matches, cannon fuses, and model rocket igniters as well as timing devices built from mechanical alarm clocks for the propane bombs. During the massacre, they carried match strikers taped to their forearms for easy ignition of the pipe bombs and CO2 bombs.
Harris also experimented with napalm, and envisioned a kind of backpack and flamethrower. They both attempted to get another friend and coworker, Chris Morris, who was a part of the Trench Coat Mafia, to keep the napalm at his house, but he refused. Harris also tried to recruit him to be a third shooter but played it off as a joke when rebuked.
Pipe bombs
Harris's website contained instructions on making pipe bombs and Molotovs, and the extensive use of shrapnel. Harris's father once discovered one of his pipe bombs. Harris's journal logged the creation of 25 pipe bombs.
Klebold scared his coworkers by once bringing a pipe bomb into work. They would give various nicknames to their pipe bombs. After the massacre, two pipe bombs had been left in Klebold's bedroom, one named "Vengeance" and another "Atlanta", presumably after the Olympic Park bombing.
Cafeteria bombs
They had in their possession eight propane tanks all converted into bombs. The weekend before the shooting, Harris and Klebold bought two propane tanks and other supplies from a hardware store. They bought six propane tanks on the morning of the attack. Harris was caught on a gas station security camera at 9:12 a.m. buying a propane tank. Both cafeteria bombs included a single 20-pound (nine kg) tank, attached pipe bombs, and supporting gasoline canisters alongside.
Car bombs
Both car bombs were made from two 20-pound propane tanks, pipe bombs, and various containers filled with gasoline were spread throughout the vehicles. Eight pipe bombs were placed in Klebold's car, and one in Harris's.
Knives
Harris and Klebold were both equipped with two knives each, but investigators have concluded that they were not used during the massacre. Harris had a boot knife on his belt and a "Khyber-pass" machete bowie knife taped to the back of his ankle. Both had an "R", referencing Harris's alias "REB", etched into the handle, and the machete had a swastika on the sheath. Klebold had a "Cobra" knife mounted to his belt on the left side as well as a switchblade in his right pocket.
Massacre
According to the shooters' respective journals and video tapes, it is believed by investigators that the pair intended to detonate their propane bombs in the cafeteria at the busiest lunch hour, killing hundreds of students. After this, they would shoot and stab survivors, as well as lob bombs. Bombs set in their cars in the parking lot would also eventually detonate, killing more students as well as any police officers, paramedics, firemen or reporters who had arrived at the school. However, the bombs in the cafeteria and cars failed to detonate.