A 17-year-old student is being held on murder charges in Friday's attack at the high school in Santa Fe, which is about 30 miles (50 kilometers) southeast of Houston.
The teenager accused of killing 10 people at a Texas high school exchanged "a lot of firepower" with police before he surrendered, a county official has said.
The shooting was the nation's deadliest such attack since the massacre in Florida that gave rise to a campaign by teens for gun control.
"The scariest thing is hearing a teacher who knows your name personally call you by your name and tell you to run", Harris tweeted. Authorities offered no immediate motive for the shooting. Pagourtzis told an investigator he acted alone and spared people he liked because he wanted his story told, the probable cause affidavit says. The governor said the assailant meant to kill himself but gave up and told police that he did not have the courage to take his own life.
On Friday morning, Santa Fe High School, southeast of Houston, became the scene of the fourth-deadliest mass shooting at a USA public school in modern history, joining a long list of US campuses where students and faculty have fallen victim to gunfire.
"We were on the ground, all piled up in random positions", he said. "I've always kind of felt like that eventually it was going to happen here too", Santa Fe student Paige Curry said.
"I was in the history hallway, and as soon as we heard the alarms, everybody just started leaving, following the same procedure as".
Fleeing students were huddled onto fields away from the school as frightened parents raced to the scene looking for terrified children.
A Colorado man says his nephew was among the 10 people who were killed in the mass shooting at a Texas high school. Six students were taken to Clear Lake Regional Medical Center.
The suspect was identified as Dimitrios Pagourtzis, who appeared to have no prior arrests or confrontations with law enforcement.
A judge denied Pagourtzis bond and took his application for a court-appointed attorney.
McCaul, a former federal prosecutor, said he expects the Justice Department to pursue additional charges, possibly involving weapons of mass destruction.
He quit playing football on the school's junior varsity squad last fall and danced as part of a church group.
Pagourtzis had recently posted a picture of a T-shirt reading "Born to Kill" on his Facebook page and he followed a number of accounts on Instagram like "sickguns" and "gunspictures", Abbott said, but classmates described Pagourtzis as a quiet, avid video game player who routinely wore a black trench coat and black boots to class. The alleged shooter used a shotgun and a.38 revolver legally owned by his father, Gov. Greg Abbott told reporters. Investigators were determining whether the shotgun's shortened barrel was legal, Texas Sen. But he says the canisters had no detonation device and the pressure cooker had no explosive material.
While cable news channels carried hours of live coverage, survivors of the February 14 Florida attack took to social media to express grief and outrage.
The suspect in the Texas school shooting began his attack by firing a shotgun through an art classroom door, shattering a glass pane and sending panicked students to the entryway to block him from getting inside, witnesses said.
Clayton County Schools Safety Chief Thomas Trawick says shots were fired in a Mount Zion High School parking lot after an argument between people who had attended a graduation ceremony for the Perry Learning Center, which prepares students for careers as an alternative to traditional high schools. This is the 22nd school shooting just this year.