Investigators, meanwhile, are scouring his journal, a computer and a cellphone that Mr. Abbott said showed the suspect had been planning the attack, and his own death.
On Friday, authorities intended to question two other people: One was at the scene and had “suspicious reactions,” according to the governor, and another had drawn the scrutiny of investigators.
Mr. Pagourtzis had no known confrontations with law enforcement, Mr. Abbott added. “As far as having a criminal history, he has none. His slate is pretty clean.”
In many ways, Mr. Pagourtzis was a part of the Santa Fe community.
He made the honor roll. He played defensive tackle on a school football team that was the pride of the town. His family was involved in the Greek Orthodox Church.
Valerie Martin, a teacher at the junior high school in Santa Fe, said she had Mr. Pagourtzis in her pre-A.P. language arts class last year.
She saw no signs that Mr. Pagourtzis might do such a thing, she recalled in an interview. She viewed him as bright, she said, adding he had taken part in the school’s competition for a national history contest. “He was quiet, but he wasn’t quiet in a creepy way.”
Tyler Ray, 18, a football player who said he knew the Pagourtzis family well, said that Mr. Pagourtzis showed up for summer workouts and tried hard even though he wasn’t very athletic. His family, Mr. Ray said, came to the games to support him, though they struggled to pay for equipment.
The day before the shooting, Mr. Ray and Mr. Pagourtzis went on a class field trip to Schlitterbahn, a water park in Galveston.
On Friday, though, a different young man showed up at school in Santa Fe.
In the art room, Zachary Muehe, a sophomore, was engrossed in his phone. He heard several booms and whipped around to see Mr. Pagourtzis, who was wearing the coat and the “Born to Kill” T-shirt.
Mr. Muehe said Mr. Pagourtzis had begun shooting as soon as he entered the classroom.
“It was crazy watching him shoot and then pump,” Mr. Muehe said. “I remember seeing the shrapnel from the tables, whatever he hit, I remember seeing the shrapnel go past my face.”
Mr. Muehe immediately tried to escape. He and his friends went to a back door in the classroom, which leads to a small courtyard, but the door was locked.
He went next to a ceramics closet that connects his classroom to another art classroom, and took one more look at the classroom behind him, and saw students lying on the ground.
“There was a girl on the ground,” Mr. Muehe said, “and he shot her in the head one or two times.”
“I just started running, as fast as I could to the other side of the campus,” he said. “When I got to the main part I started banging on the door and I saw one of my teachers. I say, ‘Hey, we’ve got a gun, everyone needs to get out.’”
Mr. Muehe’s mother, Christina Muehe, said that by Friday evening the entire community had been broken.
“There’s kids that are missing right now. You know they’re the ones that are probably dead. It’s gut wrenching,” Ms. Muehe said, adding she was deeply proud of her son for warning others about the danger unfolding inside the school.
