High school shooter studied mass shootings: Sources

Dimitrios Pagourtzis, 17, who fatally shot 10 and injured 13 others at a Texas high school, researched tactics used by other mass shooters, sources told ABC News.
4:14 | 05/21/18

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Transcript for High school shooter studied mass shootings: Sources
The parkland students there at the billboard music awards last night and Kelly Clarkson making that statement saying we need action, not silence. After yet another deadly high school shooting. Michael is there at Santa fe high school as the community tries to find a way to move forward. The gunman killed ten people mostly students, wounded 13 more. This is the ninth fatal school shooting so far this year, not even half over and with this stunning fact, 2018 has been a deadlier year for schoolchildren than for active military Servi members. That is powerful and incredible. As expected, vigils have been held over the weekend to honor all of those lives lost and, Michael, he is there this morning with their families and so many are demanding change across the world. Reporter: That's right. So many are demanding change. This school seems like it was prepared for something like this to happen, they had a shooting plan, they practiced active shooter drills, they even had two armed officers in the halls but it still wasn't enough to stop that deadly rampage. We're going to hear from some of the brave students who survived in just a moment but first let's go to ABC's Marcus Moore for the very latest on the investigation and the wounded who are fighting to recover this morning. Good morning, Marcus. Reporter: Michael, good morning to you. I'm just outside the hospital where many of the injured were treated. This morning some are still recovering after Friday's deadly school shooting. This morning, still fighting for his life after Friday's deadly rampage John Barnes, a school ct police officer who confronted the alleged shooter hailed as a hero. He doesn't want to be called a hero. His wife said he's going to hate this but he is. Reporter: Also hospitalized and listed in good condition, substitute teacher Flo rice. She is recovering from multiple gunshot wounds. This as overnight the investigation into what happened at this Texas high school enters a new phase. He's actually shooting. He's in the art room. We've got shots fired right now. Reporter: 17-year-old dimitrios pagourtzis stormed into a morning art class here at Santa fe high school yelled surprise then used a shotgun and a 38 revolver to gun down fellow students. Next thing you know everybody looks and you hear boom, boom, boom and I just ran as fast as I could. Reporter: In a startling revelation sources telling news that investigators believe the 17-year-old junior may have studied previous mass shootings allegedly incorporating aspects of those massacres into his own attack. Authorities say he had homemade explosives and wore a trench coat also a hallmark of gunmen in the columbine massacre. On his Facebook page last month he posted this photo of a t-shirt saying born to kill. Sadie Rodriguez believes her 16-year-old daughter Shana fisher was killed for rejecting him after he pursued her for months. She finally stood up to him because he kept getting more aggressive. Reporter: This morning, new video posted by TMZ showing the alleged shooter participating in a group dance during a Greek festival just last weekend. I was just shocked and surprised. Reporter: Sophomore Clayton George played with him on the cool football team. George says the alleged gunman always had a trench coat but otherwise seemed like a Normal kid. He never seemed angry at all. He always seemed calm and cool and he never even would think about hurting anyone off the football field, of course. Reporter: The sophomore like so many others searching for answers. Never in my life would I have assumed it would be him. Reporter: Now this community reeling as it remembers the lives of so many lost. The suspect's attorney said that any talk about a possible motive at this point is pure speculation but, Michael, that is the question so many in this community have as they begin the process of trying to heal. All right, thank you, Marcus. I know there's so many questions that need to be answered. When you get here it just seems like any other high school in America. There are signs that say pray for Santa fe and that makes you realize that it's anything but and they do need all of our prayers. That is for sure. Going to go back to you guys in New York. That is definitely for sure, Michael. It's been so much loss in that community.

This transcript has been automatically generated and may not be 100% accurate.

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