SANTA FE, Texas (AP) — The suspect accused of attacking a Texas high school exchanged “a lot of firepower” with authorities before he surrendered, a top county official said Saturday, a day after the shooting in an art classroom that killed 10 people.

In addition to a shotgun and a handgun, Dmitrios Pagourtzis also had several kinds of homemade explosive devices, but they were not capable of detonating, said Mark Henry, the Galveston County judge, who is the county’s chief administrator.

Investigators found a group of carbon dioxide canisters taped together, and a pressure cooker with an alarm clock and nails inside. But the canisters had no detonation device, and the pressure cooker had no explosive material, Henry said.

Authorities offered no motive, but they said in a probable-cause affidavit that the suspect had admitted to carrying out the shooting.

The gunman told police that when he opened fire, he avoided shooting students he liked “so he could have his story told,” the affidavit said.

Pagourtzis, who appeared to have no prior arrests or confrontations with law enforcement, made his initial court appearance on murder charges Friday by video link from the Galveston County Jail. A judge denied bond and took his application for a court-appointed attorney.

The shooting unfolded in Santa Fe, a city of about 13,000 people roughly 30 miles (48 kilometers) southeast of Houston.

It was the nation’s deadliest such attack since the Florida massacre that killed 17 and energized the teen-led gun-control movement. It was also the deadliest assault in Texas since a man with a semi-automatic rifle attacked a rural church late last year, killing more than two dozen people.

Meanwhile, students were being let back inside Santa Fe High School to gather belongings they abandoned when the gunfire began.

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. Braun and other officials declined to answer questions about the investigation.

Although most of the dead had not been publicly identified, relatives and acquaintances said the fatalities included a substitute teacher and a foreign exchange student from Pakistan.

Another 10 people were wounded. The wounded included a school police officer who was the first to confront the suspect and got shot in the arm. Hospitals reported treating a total of 14 people for injuries related to the shooting. Two were listed in critical condition Saturday at the University of Texas Medical Branch, the hospital tweeted.

The gunman yelled “Surprise” before he started shooting, according to Texas Rep. Michael McCaul, the chairman of the House Homeland Security Committee.

McCaul, a former federal prosecutor, said he expects the Justice Department to pursue additional charges, possibly involving weapons of mass destruction.

Pagourtzis played on the junior varsity football team and was a member of a dance squad with a local Greek Orthodox church. Acquaintances described him as quiet and unassuming, an avid video game player who routinely wore a black trench coat and black boots to class.

The suspect obtained the guns from his father, who owned them legally, Gov. Greg Abbott said. It was not clear whether the father knew his son had taken them.

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Follow AP’s coverage of the Santa Fe High School shooting here: https://apnews.com/tag/Schoolshootings .