The Santa Fe shooter exchanged gunfire with police officers for roughly 15 minutes, an official said.
The suspect, Dimitrios Pagourtzis, intended to kill himself after the shooting spree on Friday, but backed out and surrendered to police, authorities said.
Pagourtzis is being held on a capital murder charge. He confessed to the killings, court documents show.
The gunman who fatally shot 10 people at his Texas high school on Friday exchanged gunfire with police for roughly 15 minutes before surrendering, an official told The New York Times.
The suspected shooter, 17-year-old Dimitrios Pagourtzis, had intended to kill himself but apparently lacked the courage, authorities said.
"He decided to chicken out of that and came out with his hands up," County Judge Mark Henry told the newspaper on Saturday. "The investigator said there were a lot of shell casings from both sides."
Pagourtzis is being held in the Galveston County Jail without bond on a capital murder charge.
When he entered the Santa Fe High School on Friday morning, Pagourtzis was armed with two firearms, including a shotgun and a .38-caliber revolver, Gov. Greg Abbott told news outlets on Friday afternoon.
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Both weapons appeared to have been legally purchased by Pagourtzis' father, and Abbott said there was no information to suggest that he knew his son had obtained them.
Several law-enforcement officers were also praised on Friday for quickly confronting Pagourtzis. Abbott called the officers "heroes" on Friday and said their actions "probably ensured that more lives were not lost."
In the hours after the shooting, authorities had also rushed to locate a number of explosive devices Pagourtzis had allegedly left at the school and the surrounding areas, but Henry told The Times that they ended up being harmless.
The devices included a pressure cooker bomb that contained an alarm clock and nails but no explosive material, as well as a carbon dioxide device that was also harmless, Henry said.
"They were of absolutely of no harm or danger to anyone," he added.
After Pagourtzis made his first court appearance late Friday, an affidavit showed that he had surrendered to police around 8:02 a.m., roughly 30 minutes after police responded to the shooting. Pagourtzis waved his Miranda rights and confessed to the killings.
The affidavit also said Pagourtzis told investigators "he did not shoot students he did like so he could have his story told."
Bryan Logan contributed reporting.