Teen gunmen unleashed horror at Columbine in 1999

On April 20, 1999, two teenage gunmen dressed in black trench coats went on a rampage at Columbine High School in suburban Denver.

They shot and killed 12 classmates and a teacher and wounded two dozen others in what was then the deadliest U.S. school shooting. The boys then took their own lives.

The shooting shocked the country as it played out on TV news shows from coast to coast. Images from the scene showed terrified students fleeing the school, SWAT officers waiting to enter and an injured boy trying to escape through a window.

In this April 20, 1999 photo, members of a police SWAT march to Columbine High School in Littleton, Colo., as they prepare to do a final search of the school. Twelve students and a teacher died in the shootings before two teenage gunmen committed suicide. (AP Photo/Ed Andrieski)

Unidentified young women head to a library near Columbine High School where students and faculty members were evacuated after two gunmen went on a shooting rampage in the school in the southwest Denver suburb of Littleton, Colo., Tuesday, April 20, 1999. Police called the rampage a suicide mission. (AP Photo/Kevin Higley)

SWAT members run down Pierce Street while a Jefferson County, Colo., Sheriff's Department deputy peers through a fence to keep an eye on Columbine High School after a pair of gunmen went on a shooting rampage inside the facility, Tuesday, April 20, 1999, in the southwest Denver suburb of Littleton, Colo. (AP Photo/David Zalubowski)

A woman embraces her daughter after they were reunited following a shooting at Columbine High School in Littleton, Colo., on Tuesday, April, 20, 1999. (AP Photo/Ed Andrieski)

Students from Columbine High School are led away from the facility after two gunmen went on a shooting rampage Tuesday, April 20, 1999, in the southwest Denver suburb of Littleton, Colo. (AP Photo/David Zalubowski)

Kate Moulton, left, is reunited with her daughter Lauren, 14, after a shooting at Columbine High School in Denver on Tuesday, April, 20, 1999. Two young men dressed in long, black trench coats opened fire in the suburban high school, scattering students as gunshots ricocheted off lockers. (AP Photo/Ed Andrieski)

This aerial shows the news media compound near Columbine High School in Littleton, Colo., Wednesday, April 21, 1999. Media from around the world poured into the area after 15 people were killed during a shooting spree inside the school. (AP Photo/Ed Andrieski)

From left, Rachel Ruth, Rhianna Cheek and Mandi Annibel, all 16-year-old sophomores at Heritage High School in Littleton, Colo., console each other during a vigil service in Denver's Civic Center Park late Wednesday, April 21, 1999, to honor the victims of the shooting spree in Columbine High School in the southwest Denver suburb of Littleton on Tuesday, April 20, 1999. (AP Photo/Laura Rauch)

A boy looks through the fence at the Columbine High School tennis courts in Littleton, Colo., Saturday, April 24, 1999. Thirteen roses were placed on the fence in remembrance of the 13 people killed by two gun wielding students at the school, Tuesday, April 20, 1999. (AP Photo/Eric Gay)

Unidentified students embrace each other at a makeshift memorial for their slain classmates at Columbine High School on a hilltop overlooking the school in Littleton, Colo, Saturday April 24, 1999. Twelve students and a teacher were killed in a murderous rampage at the school by two students who killed themselves in the aftermath. (AP Photo/Bebeto Matthews)

The casket bearing Columbine High School shooting victim Rachel Joy Scott is signed with notes of remembrance from family members as it sits at the Trinity Christian Center in Littleton, Colo., as shown in this April 24, 1999 photo. At public gatherings of grief, such as the ones following the Columbine shootings and the Texas church massacre, more and more people are signing coffins that were made for messages. (AP Photo/Rick Wilking)

A young girl holds a rose as she is held during prayer at a memorial service on Sunday, April 25, 1999, for the victims of the Columbine High School shooting rampage in Littleton, Colo. (AP Photo/Eric Gay)

A participant at a memorial service for the victims of the Columbine High School shooting rampage holds a "NO GUNS" sign in Littleton, Colo., on Sunday, April 25, 1999. (AP Photo/Eric Gay)

Colorado Governor Bill Owens and his wife Frances pay their respects at a memorial wreath after a community wide service in Littleton, Colo., Sunday, April 25, 1999 for the victims of the shooting spree at Columbine High School. (AP Photo/Laura Rauch)

Frank Deanglis, the principal of Columbine High School, attends a community-wide memorial service on Sunday, April 25, 1999, in Littleton, Colo., for the victims of the shooting rampage at the school. (AP Photo/Khui Bui)

An unidentified mourner pauses to pray in front of the casket of Kyle Velasquez during funeral services in Littleton, Colo., Tuesday, April 27, 1999. Velasquez was killed during a shooting rampage at Columbine High School. (AP Photo/Laura Rauch)

Sally Jessy Raphael talks to John Ungerland, second left, a 17-year-old Columbine High School junior, during the taping of her program in New York, Tuesday April 27, 1999. Ungerland claims to have seen two youths, one armed, leaving the school during the shootings in Littleton, Colo. Tuesday April 20, 1999. Also on the show, scheduled to air Friday April 30, 1999, are from left, Trevor, a Goth, Matt Nalty, hidden, and Jim Brunetti, right. Nalty and Brunetti are two of three people detained by police who thought they were involved in the shootings. (AP Photo/Richard Drew)

Candles burn at a makeshift memorial near Columbine High School, Tuesday, April 27, 1999 for each of the of the 13 people killed by Eric Harris and Dylan Klebold during a shooting spree at the Littleton, Colo. school. (AP Photo/Michael S. Green)

Standing on a hill above Columbine High School in Littleton, Colo., Krista Sleeth, Bev Fleer, and Cindy Sleeth hug during a moment of silence Tuesday, April 27, 1999 for the victims of the shooting spree at school. Krista, Bev and Cindy are three generations of the same family. (AP Photo/Michael S. Green)

An unidentified woman looks at 15 crosses posted on a hill above Columbine High School in Littleton, Colo. Wednesday, April 28, 1999 in remembrance of the 15 people who died during a shooting rampage at the school. (AP Photo/Eric Gay)

John Tomlin consoles his wife Doreen while their daughter Ashley watches the funeral of John Robert Tomlin at the Community United Methodist Church in Waterford, Wis., Wednesday, April 28, 1999. Tomlin was killed in the library at Columbine High School in Littleton, Colo., when two students entered the school with guns and bombs. (AP Photo/Morry Gash)

Kacey Ruegsegger, 17, is wheeled from a Denver hospital by Patty Anderson, center, after being released on Saturday, May 1, 1999. Walking beside her are her parents Greg, left, and Darcy, right. Kacey was shot in the shoulder during the shooting rampage at Columbine High School on April 20. (AP Photo/Ed Andrieski)

Mourners visit a memorial of crosses on a hill overlooking Columbine High School in Littleton, Colo., on Saturday, May 1, 1999. Only 13 crosses stood at the site Saturday morning after Brian Rohrbough, the father of shooting victim Daniel Rohrbough, removed the crosses of suspects Eric Harris and Dylan Klebold and destroyed them. (AP Photo/Ed Andrieski)

Demonstrators gather on the Colorado State Capitol grounds in Denver, Colo., on Saturday, May 1, 1999, to protest against the National Rifle Association's annual meeting, which is being held in the city. The convention was planned long before the recent shootings at nearby Columbine High School, and the association has scaled the event down in the wake of the tragedy. (AP Photo/Eric Gay)

A large banner welcomes Columbine High School students as they arrive for classes at Chatfield High School in Littleton, Colo., on Monday afternoon, May 3, 1999. It was the first day back to school for the Columbine High School students since the April 20 shooting rampage that left 14 students and one teacher dead. Chatfield High School will be shared by students from both schools for the remainder of the school year. (AP Photo/Ed Andrieski)

Lance Kirklin, center, shares a laugh with his parents, Mike, left, and Dawn during a news conference at Denver Health Medical Center on Friday, May 14, 1999. Kirklin, 16, a Columbine High School sophomore, was shot five times during the shooting rampage at the school that left 15 dead, including the gunmen. (AP Photo/Ed Andrieski)

Tape marks the line in front of the doors to the library in Columbine High School as members of the media took their first trip through the school in the southwest Denver suburb of Littleton, Colo., Tuesday, June 15, 1999, since it was the scene of the worst school shooting spree in the history of the United States on April 20. (AP Photo/David Zalubowski)

President Clinton is joined by students from Colorado's Columbine High School in an effort to urge Congress to pass gun control legislation during a ceremony on the South Lawn of the White House, Thursday July 15, 1999. (AP Photo/Susan Walsh)

Tom Mauser, center, father of one of the students killed in the massacre in Columbine High School, joins David Winkler, left, and Ben Gelt, right, leaders of a student group called SAFE Colorado, at a news conference, Friday, July 30, 1999, west of Littleton, Colo., at which the trio asked members of Congress to include gun-control measures in juvenile justice legislation. (AP Photo/David Zalubowski)

Students sing their praise to God during a youth inspirational rally "Columbine and Friends," at Fiddler's Green Amphitheater in Englewood, Colo., Saturday night, August 14, 1999, in the wake of the Columbine High School shooting. (AP Photo/Ed Andrieski)

Columbine High School shooting victim Sean Graves, center, cuts the ribbon to welcome reporters and photographers into his parents' home that has been modified to be accessible to wheelchairs early Thursday, Aug. 26, 1999, in the southwest Denver suburb of Littleton, Colo. Close to 45 trade organizations have spent the past two months to prepare the house for Graves, who was left paralyzed from the waist down after being shot during the shooting spree at Columbine High School on April 20, 1999. (AP Photo/David Zalubowski)

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