The Columbine High School shooting’s 20th anniversary is commemorated with memorials and vigils

(AP Photo/David Zalubowski) Will Beck, right, a sophomore at Columbine High School who escaped during the shooting attack nearly 20 years ago, joins his family during a vigil at the memorial for the victims of the massacre Friday, April 19, 2019, in Littleton, Colo.

Twenty years ago Saturday, two gunmen claimed the lives of 13 victims and marked the beginning of an era in which America has repeatedly been forced to reckon with the threat of school shootings. Since the Columbine High School massacre, more than 226,000 students at 233 schools have been impacted by school shootings, according to a Washington Post analysis.

On April 20, 1999, two Columbine seniors, Eric Harris and Dylan Klebold, carried out a planned attack at their high school using a combination of firearms and homemade explosives. They shot and killed 13 people - twelve students and a teacher - before turning their weapons on themselves.

A memorial was designated in 2007 to honor the victims: students Cassie Bernal, Steven Curnow, Corey DePooter, Kelly Fleming, Matthew Kechter, Daniel Mauser, Daniel Rohrbough, Rachel Scott, Isaiah Shoels, John Tomlin, Lauren Townsend and Kyle Velasquez, and teacher Dave Sanders. The outdoor space, which sits in a park adjacent to Columbine High School, welcomes visitors to reflect on the community's loss.

This past week, three days of commemorative events were planned in their honor, culminating with Saturday's memorial ceremony in Littleton, Colorado, a Denver suburb. The events continued despite a threat against the school that arose earlier this week: On Tuesday, the community faced danger once again after an 18-year-old woman traveled from Florida to Colorado and purchased a pump-action shotgun at a shop near Columbine High School.

The woman, Sol Pais, had left a trail of disturbing messages online. A manhunt ensued and the Jefferson County Public Schools ordered a lockout, keeping students inside for safety. As the manhunt stretched into a second day, classes were canceled. Pais was found dead of an apparent self-inflicted gunshot wound.

The incident heightened already tight security measures around the week's events.

Bailey Rosiere was just a second-grader when the Columbine came under siege; she was one of hundreds who attended a vigil on Friday night at the Columbine Memorial. Despite two decades of distance from the event, she told a local ABC station that the memory would never leave her:

"It makes it not just an empty or upsetting or sad feeling; it's more of a deep impact," she said. "Because you can't ever forget no matter how young you were."

Also in the crowd was Sarah Boyd, who came to lay flowers with her husband as she has done every year.

“It can happen anywhere. No one is immune, unfortunately,” Boyd told the Denver Post. She had graduated from Columbine in 1996 and was nearby when the attack began. “I hope someday that people can look back and say these are the things that were made better because of such a terrible day.”