The few disturbing signs Columbine High School shooter Dylan Klebold showed before he massacred 13 at his school along with his friend didn't elicit his mother's concern, she said at a talk Friday. 

Sue Klebold said that before a theft arrest in high school and school suspension due to hacking into computers to break into another students' locker, Dylan Klebold seemed to be a happy young man—one she called "Sunshine Boy."

In retrospect, his mother noted signs that she didn't think much of at the time and urged students at a packed talk Friday in Reynolds Theater to be aware of the signs of suicide. One example warning sign she noted was a person offering their belongings to another if "something bad were to happen." 

“I think we like to believe that our love and our understanding is protective, and that ‘if anything were wrong with my kids, I would know,’ but I didn’t know, and I wasn’t able to stop him from hurting other people. I wasn’t able to stop his hurting himself and it’s very hard to live with that," Klebold told ABC News.

Sue Klebold has dedicated much of her time since the shooting to raising awareness for mental health issues. In 2016, she published her memoir A Mother’s Reckoning: Living in the Aftermath of a Tragedy, which describes that she did not identify the depression her son suffered in his teenage years.

She said that she donates all proceeds from the memoir to mental health organizations, but does accept payments to talk at events like the one at Duke in order to sustain her advocacy. 

She also gave a TED Talk in 2017 in which she relates her story and advocates for wider awareness on the topic. 

Klebold started the Friday talk by immediately addressing the details of the shooting. Soon after, she discussed the long term physical and psychological effects on the more than 20 people left injured, the grief of the families of lost ones and other, less publicized effects, such as the devastating infringement upon life in the wider Columbine community. 

Klebold asserted that her depressed son became a danger to the public because he wanted to end his own life, but also because of his pairing with his accomplice and friend Eric Harris, a person that "wanted to kill." 

Klebold related her personal story—fraught with attacks from those in her community—and expressed what she said she had learned in the nearly 20 years since the shooting. Her own harrowing personal story, she said, was an example for why one should take a more proactive role in providing resources to those that may be suffering. 

First-year Nithin Ragunathan said that it was “interesting to see that she has turned her life in a direction that can help other people.” He also said that it is “nice to see the school is taking some initiative.”