Darrell Scott, the father of the first teenager shot at Columbine High School, urged a new era of teenagers today to carry on his daughter Rachel's "chain reaction" of doing good to others.

"Make a list of seven to ten people closest to you," Scott told 1,400 students at Castle View High School in Castle Rock. Then "over the next three days, simply tell them how much you appreciate them, love them, care about them. I promise you they will never forget it."

Ten years ago this April, Rachel Scott and twelve others were killed in the worst mass high school shooting in U.S. history. Since then, Scott, 59, has spoken to an estimated 10 million people, including than more than a million high school students, about motivating themselves to practice "Rachel's Challenge," the message of loving others and doing good in the world which Rachel was expressing in her diaries and to others right up to hours before her death.

This afternoon, Scott will hold workshops at the high school. The public is invited to a 7 p.m. workshop at the school.