An exchange student from Pakistan is among the first named victims of a Texas high school shooting.
Ten people were killed and 10 were injured at Santa Fe High School when a student opened fire. The suspect is Dimitrios Pagourtzis, 17.
The embassy of Pakistan in Washington DC confirmed that student Sabika Sheikh was among the dead.
Substitute teacher Cynthia Tisdale was also killed in the attack, her family told US media outlets.
Mrs Tisdale's niece and brother-in-law both confirmed the news. Writing on Facebook, John Tisdale said his sister-in-law was an "amazing person".
Sabika Sheikh, aged 17, had been on the Kennedy-Lugar Youth Exchange & Study Abroad programme (YES). The programme is run by the US state department, and was set up in the aftermath of the 11 September 2001 attacks to bring students from Muslim-majority nations to the US on a cultural exchange.
Her parents, Abdul Aziz and Farah Sheikh, told the BBC they heard about the shooting through television news.
They said they confirmed their daughter's death within an hour by speaking to school administrators. Ms Sheikh's body would be returned to her home in Karachi early next week, they said.
Other victims, believed to be mostly students, are expected to be identified by Texas authorities later on Saturday.
The attacker, Dimitrios Pagourtzis, was arrested and charged with murder. He allegedly used a shotgun and a revolver taken from his father, who legally owned the weapons.
What happened during the attack?
Students said the shooter entered an art class and opened fire shortly before 08:00 (13:00 GMT) on Friday. There were 1,400 students in the school at the time of the attack.
One student, Breanna Quintanilla, told AP that Mr Pagourtzis walked into the room, pointed at someone, and announced: "I'm going to kill you." Ms Quintanilla was wounded in her leg as she fled.
Officers stationed at the school engaged Mr Pagourtzis. One of them, John Barnes, was injured. He was in a critical condition and undergoing surgery, local media reported.
Police also found information in the suspect's diary, and on his computer and mobile phone, suggesting that he planned the attack and intended to kill himself afterwards.
Texas Governor Greg Abbott said the teenager "gave himself up" because "he didn't have the courage to commit the suicide".
Mr Abbott also said "various kinds of explosive devices" had been found at the school, 40 miles (65km) south of Houston, and off-campus. They included "a CO2 device" and "a Molotov cocktail", he said.
So far this year, more than 5,000 people have died in shooting incidents in the United States, according to monitoring group the Gun Violence Archive.
Hundreds of people gathered at sunset on Friday on a large open lawn near the school for a vigil.
The sound of preachers and politicians was intermittently drowned out by wailing and sobs from attendees, the BBC's Paul Blake said.
President Donald Trump, speaking at a prison reform event at the White House, described the attack as "absolutely horrific".
"My administration is determined to do everything in our power to protect our students, secure our schools, and to keep weapons out of the hands of those who pose a threat to themselves, and to others," he said.
The White House school safety panel - set up in the aftermath of the mass school shooting in Parkland, Florida, earlier this year- had been "activated" and would meet next week, the White House said.
Governor Abbott called the shooting "one of the most heinous attacks that we've ever seen in the history of Texas schools".
One professional athlete from the state - JJ Watt, of the Houston Texans NFL team - has offered to pay the funeral expenses of the victims.
How does it compare with previous school shootings?
The Texas attack is the deadliest school shooting since a student opened fire in February at Marjory Stoneman Douglas High School in Parkland, Florida, killing 17 people.
That assault spawned a nationwide youth-led campaign for gun control, and a litany of proposed changes:
- President Trump moved to ban so-called bump stocks, used in last year's Las Vegas shooting
- Congress is considering the Stop School Violence Act to provide increased security such as metal detectors in schools
- Mr Trump has endorsed arming teachers - a long-held position of the National Rifle Association (NRA)
Gun control advocates have criticised what they see as minor changes amid continued support for the NRA from leading politicians.
The worst school shooting in US history occurred at Virginia Tech university in 2007, where 33 people were killed and 25 injured.
There have been more deaths in US school shootings so far in 2018 than there have been deaths in the US military, according to an analysis by the Washington Post.
What do we know about the attacker?
Authorities said journals kept by Mr Pagourtzis, 17, showed that he planned to carry out the attack and intended to kill himself afterwards.
But Mr Abbott told reporters that, unlike several previous mass shootings, authorities had not been alerted to Mr Pagourtzis before the attack on Friday.
"Unlike Parkland, unlike Sutherland Springs, there were not those types of warning signs," Mr Abbott said. "We have what are often categorized as red-flag warnings, and here, the red-flag warnings were either nonexistent or very imperceptible."
Mr Pagourtzis suggested in social media posts that he was an atheist and said: "I hate politics". On 30 April he posted a photograph of a T-shirt bearing the slogan "Born to Kill".
He is being held at Galveston County Jail on a charge of capital murder.