It was the morning of what would become known as the Columbine shooting.
On April 20th, 1999, Susan Klebold heard her son, Dylan Klebold, getting up for the day and leaving the house.
"Dylan?" she shouted.
"Bye," he replied.
That was the last time she heard from her 18-year-old son.
Dylan Klebold, and 17-year-old Eric Harris, entered the Columbine High School just after 11 a.m. armed automatic weapons. They killed 13 people before ending their own lives.
Susan Klebold is now an advocate for mental health, hoping to break stereotypes about depression, and spread awareness for those who are suffering.
To learn about mental illness or for information on resources available, click here.
Watch the video above to listen to the interview with Susan Klebold.