Columbine anniversary Police stand outside the east entrance of Columbine High school as bomb squads and SWAT teams secure students April 20, 1999, in Littleton, Colorado, after two masked teens on a "suicide mission" stormed the school and blasted fellow students with guns and explosives before turning the weapons on themselves. (MARK LEFFINGWELL/AFP via Getty Images)
Columbine anniversary Students run out of the Columbine High School as 2 gunmen went on a shooting spree killing fifteen, including themselves. (Steven D Starr/Corbis via Getty Images)
Columbine anniversary Students run from Columbine High School run under cover from police April 20,1999, in Littleton, Colorado, after two masked teens on a "suicide mission" stormed the school and shot fellow students with guns and explosives before turning the weapons on themselves. (MARK LEFFINGWELL/AFP via Getty Images)
Columbine anniversary View of damage to the west entryway to Columbine High School where teen-age gunmen Eric Harris and Dylan Klebold entered the school April 20, 1999 in Littleton, CO. Flags mark points where evidence such as bullet casings were found and the photographs of the incident were released in a voluminous CD-ROM report May 15, 2000. (Getty Images/Getty Images)
Columbine anniversary Columbine Shooters Eric Harris, left, and Dylan Klebold appear on surveillance tape in the cafeteria at Columbine High School on the day of the shooting. The Jefferson County Sheriff played the video as well as videos made by the gunmen for the media after Time Magazine reported on them. (Kevin Moloney/Getty Images)
Columbine anniversary Bill Curry, left, talks no the phone with family after getting word that his daughter Kendra and niece Kami had barricaded themselves in a closet with over 20 other students at Columbine High School in Littleton, Colorado. Lorie Curry (right) and Janet Olmstead cry at the word that the girls were still in the gun-shattered school. Jason Curry (far right), waits by their sides. (Kevin Moloney/Getty Images)
Columbine anniversary Eric Harris (L) and Dylan Klebold examine a sawed-off shotgun at a makeshift shooting range March 6, 1999, in Douglas County, Colorado, in this image from video released by the Jefferson County Sheriff's Department. Approximately six weeks after this video was made, Klebold and Harris killed 13 people at Columbine High School in Littleton, CO in the worst school shooting in U.S. history at the time. Some of the weapons seen in the video were used in the shooting. (Jefferson County Sheriff's Department/Getty Images)
Columbine anniversary At the Denver Civic Center Amphitheater, at a candlelight vigil for victims of the Columbine HS shootings, Tamara Tatar writes her sentiments on a memory wall Wednesday, April 21. She is 18, and a senior at Ponderosa H.S. in Parker, Colorado. (Star Tribune via Getty Images/Star Tribune via Getty Images)
Columbine anniversary US President Bill Clinton pauses for a moment of prayer for the students and faculty of Columbine High School in Littleton, Colorado, April 21, 1999, during an address to White House Volunteers in the Old Executive Office Building in Washington DC. (JOYCE NALTCHAYAN/AFP via Getty Images)
Columbine anniversary Students Of The Columbine High School, Come To Pay Their Respects To Friends They Lost, In The Shooting Spree. (Andrew Shawaf/Getty Images)
Columbine anniversary Andrew Burgos from the Columbine High School cries as he places a panel at the Clement Park memorial site in Littleton, CO April 24, 1999. Memorial services were planned that weekend for the twelve students and one teacher killed by the two teenage gunmen at the school April 20, 1999. (HECTOR MATA/AFP via Getty Images)
Columbine anniversary Vice President Al Gore and his wife Tipper lay flowers at a wreath in Clement Park for the victims of the Columbine High School shooting after speaking at a memorial service on April 25, 1999, in Littleton, Colorado. (MARK LEFFINGWELL/AFP via Getty Images)
Columbine anniversary Flowers are left as a memorial to the victims outside Columbine High School in Littleton, Colo., where two teenagers shot to death 12 students and a teacher before killing themselves. (New York Daily News Archive/NY Daily News via Getty Images)
Columbine anniversary A student from Columbine High School kneels down in front the coffin carrying the body of teacher David Sanders during his funeral April 26, 1999 In Littleton, Colorado. Sanders and 12 students died following a shooting by two gunmen at the school on April 20, 1999. (Pool/Getty Images)
Columbine anniversary A student from Columbine High School kneels down as he pays his last respect, in front of the coffin carrying the body of teacher David Sanders during his funeral service 26 April 1999 in Littleton, Colorado. Sanders and twelve students died following a shooting by students in the school compound April 20, 1999. (RICK WILKING/REUTERS POOL/AFP via Getty Image)
Columbine anniversary Friends of the victims of the April 20, 1999, Columbine High School shooting embrace after the moment of silence observed statewide during a ceremony held at the state capital in Denver, Colorado 20 April 2000. Twelve students and one teacher were killed by two student gunmen who then committed suicide. (MARK LEFFINGWELL/AFP via Getty Images)
Columbine anniversary Two people visit a memorial in Clement Park near Columbine High School April 30, 1999 in Littleton, Colorado. The two crosses representing the gunmen Eric Harris and Dylan Klebold are now wrapped in black plastic. An anonymous note on one of the shrouds states that this is not the time or place "for the reopening of old wounds." (Steve Peterson/Getty Images)
Columbine anniversary Three unidentified Columbine High School students look at the 13 crosses memorializing those killed at their school 2 years ago after a memorial service April 20, 2001, in Littleton, Colorado. (Michael Smith/Getty Images)
Columbine anniversary Thousands visit the memorial erected for the Columbine shooting victims in Robert Clement Park near the school. There visitors paused at the cross of Dylan Klebold, one of the killers. (Kevin Moloney/Getty Images)
Columbine anniversary Fifteen crosses honoring those that died in the Columbine High School shooting rest on a hill at Clement Park. They are from left to right, Rachel Scott, John Tomlin, Steve Curnow, Lauren Townsend, Isaiah Shoels, Eric Harris, William Dave Sanders, Kelly Flemming, Matthew Kechter, Corey DePooter, Dylan Klebold, Kyle Valasquez, Daniel Mauser and Daniel Rohrbough. Both Klebold' s and Harris's cross had been covered with black plastic. (Craig F. Walker/Denver Post via Getty Images)
Columbine anniversary Craig Scott spoke at a service at Trinity Christian Center that was to honor those who were killed or wounded at Columbine High School one year ago after the shooting. (Andy Cross/Denver Post via Getty Images)
Columbine anniversary Candles wrap around a collection of flowers at the Columbine Memorial at Clement Park in Littleton, Colorado, during a community vigil for the 20th anniversary of the Columbine High School mass shooting on April 19, 2019. - 12 students and one teacher were massacred by two heavily armed students during the Columbine High School shooting on April 20, 1999. (JASON CONNOLLY/AFP via Getty Images)
Columbine anniversary Columbine High School student Mark Taylor, a victim of student gunmen Eric Harris & Dylan Klebold in their April massacre at school, with mom Donna in his bedroom decorated with well wishes sent from students around country. (Steve Liss/The LIFE Images Collection via G)
Columbine anniversary A man prays while visiting the Columbine Memorial at Clement Park in Littleton, Colorado, before a community vigil for the 20th anniversary of the Columbine High School mass shooting on April 19, 2019. - 12 students and one teacher were massacred by two heavily armed students nearly 20 years ago during the Columbine High School shooting on April 20, 1999. (Photo by Jason Connolly / AFP) (Photo credit should read JASON CONNOLLY/AFP via Getty Images) (JASON CONNOLLY/AFP via Getty Images)
Columbine anniversary Police patrol outside Columbine High School on April 17, 2019, in Littleton, Colorado, as all Denver-area schools were evacuated and classes canceled after an active threat to the area made by Sol Pais. - A US teenager has been found dead after a massive search by authorities who feared she posed a threat because of an obsession with the Columbine High School massacre, US media reported. Sol Pais, 18, had traveled on Monday from Miami to Denver where she bought a pump-action shotgun and ammunition before disappearing in the foothills around the city.US media reported police found her body at the base of Mount Evans, near Denver."There is no longer a threat to the community," the FBI's Denver office said on its Twitter account. (CHET STRANGE/AFP via Getty Images)
Columbine anniversary Police patrol outside a locked Columbine High School on April 17, 2019, in Littleton, Colorado, as all Denver-area schools were evacuated and classes canceled after an active threat to the area made by Sol Pais. - A US teenager has been found dead after a massive search by authorities who feared she posed a threat because of an obsession with the Columbine High School massacre, US media reported. Sol Pais, 18, had traveled on Monday from Miami to Denver where she bought a pump-action shotgun and ammunition before disappearing in the foothills around the city.US media reported police found her body at the base of Mount Evans, near Denver."There is no longer a threat to the community," the FBI's Denver office said on its Twitter account. (CHET STRANGE/AFP via Getty Images)
Columbine anniversary Some 70,000 people gather at a memorial service to honor the people killed in the Columbine High School shooting. (Steven D Starr/Corbis via Getty Images)
