- Video report by ITV News Washington Correspondent Robert Moore
Ten people have been killed and at least another ten wounded in a mass shooting at a Texas high school, authorities have said.
Students are thought to account for most of the dead and injured in the attack on Santa Fe High, the latest in a series of deadly school shootings in the US.
The suspected gunman has been detained by police. He was named as 17-year-old Dimitrios Pagourtzis by law enforcement sources.
Authorities have now discovered journals in which he outlined his plans for the shooting and said he also planned to take his own life, Texas Governor Greg Abbott told a press conference.
"He gave himself up and admitted at the time that he didn't have the courage to commit the suicide," Mr Abbott said.
The gunman armed himself with a shotgun and a .38 revolver, both of which are understood to have belonged to his father.
Police have also found "various different kind of explosive devices" in connection with the attack, including a Molotov cocktail.
A second student has been held as a "person of interest" and police also want to speak to a third person.
NBC affiliate KPRC reports that bomb squads are also attending a home around three miles from the school in connection with the shooting.
Students said that gunshots had rung out in the corridors and fire alarms sounded as they fled for cover.
Some wept after they escaped, saying they are scared to think of returning to classes.
"I shouldn't be going through this, this is my school," said one girl who escaped to safety by running into the woods.
"This is my daily life, I shouldn't have to feel like that and I feel scared to even go back."
Others said that such attacks could no longer come as a surprise. This is the 22nd school shooting in the US of this year alone.
"It's been happening everywhere. I've always felt like eventually it was going to happen here too," said one teenager.
The Texas Governor Mr Abbott said the suspect had a picture of a t-shirt with the slogan "Born to kill" but insisted there had been no obvious indications or suspicions that should have been acted on.
"His slate is pretty clean. There simply were not the kind of warning signs that we've seen in other shootings," he said.
He described the shooting as "probably the worst disaster ever to strike this community".
"It's impossible to describe the magnitude of the evil of someone who would attack innocent children in a school," he said.
He called for stronger action to prevent such tragedies, saying: "We need to do more than just pray for the victims and their families."
However, he did not call for strong gun controls which are backed by many victims of similar school shootings but fiercely opposed by the NRA.
President Trump offered his prayers to those affected, saying "May God be with the victims and the victim's families.
"It's a very sad day."
Speaking in Washington DC, he said: "This has been going on too long in our country, too many years, too many decades now.
He said his Government 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".
"Everyone must work together at every level of government to keep our children safe".
At least two of the injured are in critical condition, authorities reported.
Chief nursing officer Dr David Marshall at the University of Texas Medical Branch in Galveston has said that one person was undergoing surgery.
He added that a juvenile had also been admitted and a second adult is being treated in the emergency room.
A police officer is also among those being treated, but the extent of his injuries are unknown.
This is the highest death toll for a campus shooting since February, where 17 people were killed at a school in Parkland, Florida.