Ten people were killed and at least 10 injured when a student armed with a shotgun and a revolver opened fire at his Texas high school on Friday, officials said, in the latest deadly school shooting in the United States.
The gunman, who was arrested and charged with murder, was identified as Dimitrios Pagourtzis, a 17-year-old junior at Santa Fe High School in Santa Fe, Texas.
Investigators say the teenager admitted he went on a shooting rampage and that when he opened fire at Santa Fe High School on Friday morning, "he did not shoot students he did like so he could have his story told."
Most of the dead are students, police said. Governor Greg Abbott called it "one of the most heinous attacks that we've ever seen in the history of Texas schools".
"Nothing can prepare a parent for the loss of a child," Mr Abbott told reporters in Santa Fe, located some 50 kilometres southeast of Houston, as he gave an update on the death toll.
Mr Abbott said the gunman apparently carried out the attack with a shotgun and a .38 revolver belonging to his father, and that the weapons were legally owned.
The Houston Chronicle said Mr Pagourtzis was armed with pipe bombs in addition to firearms when he burst into a classroom at the start of the school day.
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The governor said searches were being conducted at two residences and "various explosive devices" were found including a "CO2 device" and a Molotov cocktail.
He said journal entries by the gunman suggested he wanted to commit suicide but "he gave himself up."
Mr Abbott also said there were no "warning signs" about the suspect ahead of time although he did post a picture on his Facebook page of a T-shirt with the words "Born to Kill" on it.
Law enforcement authorities were questioning two people including one who "may have had some level of involvement in the crime," Mr Abbott added.
Harris County Sheriff Ed Gonzalez said the "majority" of the dead were students.
"Officers inside encountered a bloody mess in the school," a senior law enforcement official told the Chronicle. "Evidently this guy threw pipe bombs all in there. We don't know if any of them went off."
The shooting was the latest in what has become an all-too-familiar situation in American schools, where gun violence has become a part of everyday life.
"My friend got shot in the art hall," a weeping Santa Fe student, Dakota Shrader, told reporters.
"I shouldn't be going through this," Ms Shrader said as her mother comforted her. "It's my school. This is my daily life. I feel scared to even go back."
Ms Shrader said fire alarms went off "and everybody just started running outside.
"And the next thing you know everybody looks and you hear 'boom, boom, boom' and I just ran as fast as I could to the nearest forest so I could hide and I called my Mom."
Earlier this year, 17 students and staff were killed at a Florida high school - a massacre that prompted survivors to launch a grassroots campaign against gun violence.
It was the second mass shooting in Texas in six months.
Twenty-six people were killed in a Texas church in November 2017 by a 26-year-old Air Force veteran.
US President Donald Trump called the latest school massacre "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," Mr Trump said at the White House.
In a tweet, he added that he grieved for "the terrible loss of life".
"We are with you in this tragic hour, and will be with you forever," he told the students and teachers of Santa Fe High School.
The shooting erupted before 8:00 am, as the first classes of the day were starting.
Student Paige Curry told local media that she heard gunshots and then a fire alarm, after which students were taken out by teachers to a nearby gas station.
"I saw some girl - she had, you know, she got shot in the kneecap, I guess. So she had a bandage around it. She was limping and then the firemen came and got her," another student, Tyler Turner, told CBS.
The school district, which quickly imposed a lockdown, cleared the students from the campus, with television footage showing them leaving in a single file.
Parent Richard Allen told KTRK TV he arrived at the school soon after the shooting and reported seeing a number of victims being taken away in ambulances.
"My son said someone went into the art room and started shooting a lot of the kids," Mr Allen said.
The Santa Fe assault comes three months after the shooting at Marjory Douglas Stoneman High School in Parkland, Florida, which sparked a student-led movement for tighter gun laws.
"We are fighting for you," tweeted David Hogg, a Stoneman Douglas student who has emerged as a leader of the gun control campaign.
"We cannot let this continue to be the norm," tweeted Delaney Tarr, another student at Stoneman Douglas. "We cannot."
Former Democratic presidential candidate Hillary Clinton urged lawmakers to take action.
"Every day that we fail to act on gun violence, we are failing our children," Ms Clinton said on Twitter. "This should be a day for soul searching across America - and that soul searching should be matched with legislating to begin dealing with this national shame."
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Also on Friday police say one person was killed and another wounded in a shooting between people leaving a high school graduation ceremony in Georgia.
A Clayton County Police statement said "one person is now confirmed deceased." It followed a ceremony for graduates of the Perry Learning Center, which prepares students for careers as an alternative to traditional high schools.
The county schools' safety chief, Thomas Trawick, says people going to their cars got into an argument that led to the shooting. He said he couldn't provide details about the injuries and had no information about any suspects.
Trawick said his initial reaction "wasn't pleasant," given that 10 people were killed earlier in the day in a school shooting in Texas.
"The last thing you want to do is have a situation at a graduation that results in anyone being injured, and definitely not being shot," he said.