We're going to turn to the mom who stopped what could have been a massacre by turning in her son. He was planning to carry out a shooting at the latest "twilight" movie. She is speak out for the first... See More
We're going to turn to the mom who stopped what could have been a massacre by turning in her son. He was planning to carry out a shooting at the latest "twilight" movie. She is speak out for the first time. And amy robach has the story. Reporter: Speaking out for the first time since turning her son into police, tricia lammers said she did what she thought was right. I am not a hero. I love my community just as much as I love my son. And I respect the people that live in my community. And also respect their safety and their right to be safe. Reporter: At a press conference late tuesday, lammers gave the first insight into the mind of her 20-year-old son, blaec, who confessed to plotting a movie theater massacre at the "twilight" screening sunday, and continued his rampage at a nearby walmart. We have been battling this since 2008. Reporter: Still, she says she feels partly responsible. I think any mom at any time would blame herself. Reporter: She became suspicious last tuesday, after finding his receipts for two weapons. Worried he may be off his medication, she contacted police. We had the suspect in custody within an hour of being notified by the family. Reporter: He told them he purchased two assault rifles and hundreds of rounds of ammo at an area walmart on monday. And got his friend to teach him how to shoot the next day. He said he planned to commit a mass shooting at this movie theater. Even purchasing a ticket to a late-night screening at the final installment of the "twilight" series, "breaking dawn part 2." I have a bad habit of underestimating you. Reporter: Meantime, lammers says she knows her son is a good kid with a good heart. Hopefully blaec will get the help he needs. Reporter: And blaec lammers made a brief appearance yesterday, where prosecutors determined he should undergo a mental health evaluation, something you heard his mother say he desperately needs. His next court appearance is EARLY NEXT YEAR, JANUARY 23rd. What a brave mom. Thanks goodness she spoke up. Thanks very much. Josh, what a story you have. Yeah.
This transcript has been automatically generated and may not be 100% accurate.