At least 10 others were wounded in the attack.
Nicholas Poehl, one of two lawyers hired by the suspect's parents to represent him, told Reuters he had spent a total of one hour with Pagourtzis on Friday night and Saturday morning.
The school's roughly 1,400 students will be allowed inside in groups of no more than 10 and would be accompanied by officers, said Walter Braun, the school district's chief of police.
"We drill all of the time with the students and staff and they're prepared to go into action".
"Our officers went in there and did what they could".
On Friday morning, Santa Fe High School, southeast of Houston, became the scene of the fourth-deadliest mass shooting at a US public school in modern history, joining a long list of USA campuses where students and faculty have fallen victim to gunfire.
The teenager, identified by law enforcement as Dimitrios Pagourtzis, has been charged with capital murder and is being held without bail in Santa Fe, Texas, where authorities said he opened fire shortly before 8 a.m. Friday.
The argument led to two women being shot, with one killed from multiple gunshot wounds to the chest.
A judge denied Pagourtzis bond and took his application for a court-appointed attorney. "He's a hero in my book".
Dmitrios Pagourtzis, 17, is suspected of storming an art classroom on Friday armed with his father's legally owned shotgun and handgun.
Early Saturday, FBI agents were seen at a blue trailer home believed to be connected to the suspect.
A top county official said the student exchanged "a lot of firepower" with police before he surrendered.
Meanwhile, students were being let back inside Santa Fe High School to gather belongings they abandoned when the gunfire began.
Grief counselors and comfort dogs were on hand at a local church where the Red Cross had opened a Family Assistance Center for those affected by the shooting.
The gunman told police he avoided students he liked "so he could have his story told". It is also unclear why the gunman targeted the art class.
Her father said: "I kept calling her and sent her messages on WhatsApp. We are gratified by the public comments made by other Santa Fe High School students that show Dimitri as we know him: a smart, quiet, sweet boy", the family said in a statement. Watt, who is originally from Wisconsin, has been playing for the Texans since 2011, and has been active in the community ever since.
He bristled at suggestions that maybe it would be safer if guns were not so readily available. "He continued to get more aggressive".
In response to the Florida killings, President Donald Trump's administration said it would step up aid to states that want to arm school employees, a move that has little support from educators.
All schools in the Santa Fe school district will remain closed on Monday and Tuesday, officials said at a short briefing.
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