At least 10 people are killed and 10 others are wounded after gunman opens fire at school in US state of Texas.

A 17-year-old boy armed with a shotgun and a revolver has opened fire at a school in the US state of Texas, killing at least 10 people and wounding 10 others, according to authorities.

The gunman, identified by police as Dimitrios Pagourtzis, was taken into custody on murder charges after the Friday morning attack at Santa Fe High School, located about 50km southeast of Houston,

Texas Governor Greg Abbott said the shooting, which took place shortly before 8am (13:00 GMT) was “one of the most heinous attacks that we’ve ever seen in the history of Texas schools”.

“It’s impossible to describe the magnitude of the evil of someone who would attack innocent children in a school,” Abbott told reporters on Friday afternoon.

“As of this time, there have been 10 lives that have been lost, and another 10 wounded,” Abbott said.

“It’s time in Texas that we take action to step up and make sure this tragedy is never repeated ever again in the history in the state of Texas,” he added.

“One or two” other “people of interest” have been detained and are being questioned by officials, according to Abbott.

The governor said the suspected shooter carried out the attack with a shotgun and a .38 calibre revolver he had apparently taken from his father, who legally owned both weapons.

#UPDATE There have been explosive devices found in the high school and surrounding areas adjacent to the high school. Because of the threat of explosive items, community members should be on the look-out for suspicious packages and anything that looks out of place. — Santa Fe ISD (@SantaFeISD) May 18, 2018

‘Everyone started running’

The suspect had also planted various types of explosives in a home and a vehicle, including a molotov cocktail, authorities said.

The 17-year-old was held without bond in the Galveston County jail on charges of capital murder, according to Henry Trochesset, county sheriff.

Wesley Hill, a student at the school, said he had been there for only about 25 minutes when police evacuated his classroom. He told the local ABC News affiliate his teacher helped lead them to safety.

“It was scary. I didn’t know what to think … My heart started beating real fast; I didn’t know what to do,” Hill said.

Another student, Dakota Shrader, said she heard an alarm sound in the high school, and then three loud booms.

“Everyone started running,” she told ABC-13 KTRK in tears and visibly shaken.

‘Horrible tragedy’

Among those wounded was one officer, who was being treated at a local hospital, Harris County Sheriff Ed Gonzalez told reporters.

At least six injured people, including the police officer, were transported to local hospitals, said Chief Walter Braun of the Santa Fe Independent School District (ISD) police.

David Marshall, chief nursing officer at UTMB hospital in Galveston, Texas, said three people – two adults, one male and one female – and one boy under 18 – were brought in with gunshot wounds.

The female patient was undergoing surgery after being shot in the leg, Marshall told reporters.

The adult male was also undergoing surgery after being shot in the arm, and the underage patient had a gunshot wound to the leg.

“It’s a horrible tragedy. Our hearts go out to those folks in Santa Fe … We’re doing the best we can to be a community partner to take care of them,” Marshall said.

Safi Madain, medical director in the ER at Clear Lake Medical Center, said eight high school students received treatment at the hospital for gunshot wounds.

Local officials called on residents to be vigilant and report any suspicious packages to the authorities.

Leigh Wall, the Santa Fe ISD superintendent, said the community had “experienced an unthinkable tragedy”.

“We have received an outpouring from across the state, and we appreciate your continued prayers for our students and our staff and our community,” Wall told reporters.

US President Donald Trump expressed “sadness and heartbreak” over the shooting.

Describing the incident as “absolutely horrific,” Trump said: “This has been going on too long in our country.”

This is the third school shooting in eight days in the US, according to CNN, and the 22nd so far this year.

A shooting at a high school in Parkland, Florida, that killed 17 students and staff in February sparked a movement for stricter gun control laws in the US.

To the students and faculty of Santa Fe High School, we are with you. #MarchForOurLives pic.twitter.com/3DYXOhmwsP — March For Our Lives (@AMarch4OurLives) May 18, 2018

Parkland students sent “love and support” to Santa Fe on Friday.

“Though this is the 22nd school shooting this year, we urge those reading this not to sweep it under the rug and forget,” the students said in a statement.

“This is not the price of our freedom. This is the most fatal shooting since the one at our school and tragedies like this will continue to happen unless action is taken.”