Twenty-three years after the Columbine High School shooting, Americans are grieving another tragic loss of life after 21 people were killed at Robb Elementary School in Uvalde, Texas. 

Darrell Scott, the father of Columbine’s first victim Rachel Scott, joined "Outnumbered" Wednesday to reflect on the horrific shooting and discuss his mission to prevent future school violence. 

"If you take the horrible winding road back through every school massacre, school shooting, it leads back to Columbine and eventually leads back to my daughter, who was the first of close to 200 students now that have been killed over the last 23 years," Scott said.

On Tuesday, 18-year-old Salvador Ramos entered Robb Elementary School and opened fire on students, killing 19 children and two teachers. Prior to entering the building, Ramos shot his grandmother. Authorities say Ramos acted alone and was shot and killed by a Border Patrol officer. Police have not yet identified a motive. 

UVALDE, TEXAS SCHOOL SHOOTING: 19 CHILDREN, 2 TEACHERS KILLED, SUSPECTED SHOOTER DEAD

Robb Elementary School sign

A state trooper walks past the Robb Elementary School sign in Uvalde, Texas, Tuesday, May 24, 2022, following a deadly shooting at the school. (William Luther/The San Antonio Express-News via AP)

As the death toll mounted throughout the day, parents and the Uvalde community searched for their children and faced the fear of losing a child. 

"One of the most horrible things is not knowing," Scott shared, remembering his own experience of losing his daughter. 

TEXAS SCHOOL SHOOTING: ALL VICTIMS IDENTIFIED, SALVADOR RAMOS' GRANDMOTHER IN SERIOUS CONDITION

Tuesday’s shooting is the deadliest school incident in the U.S. since the Sandy Hook elementary shooting in 2012. 

As school districts nationwide ramp up security, Darrell Scott offered a message of hope. 

Rachel’s Challenge, a not-for-profit organization inspired by Rachel’s legacy, works to combat school shootings by focusing efforts on the main causes of youth violence.

"There's hardening the target, but they're softening the heart," Scott said. "And our whole mission is to soften the hearts of young people because most of these school shootings are done by students themselves."

Darrell Scott and Rachel’s Challenge offer a glimmer of hope following another dark day in modern American history. 

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"There are eight school shootings we know of that would have taken place if it hadn't been for Rachel's Challenge," Scott said. 

Fox News' Greg Norman and Bill Melugin contributed to this report.