ABC News Diane Sawyer asks the Columbine shooters mother about any signs she may have missed. SUBSCRIBE to ABC NEWS: .

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Her son and his friend killed 13 people at Columbine High School almost 17 years ago. Sue Klebold has lived with guilt since — guilt for what her son did and .
The mother of Dylan Klebold speaks to Diane Sawyer in an exclusive interview to air today in a special edition of 20/20. Sue Klebold gave her first TV interview .