Two suspects, both male students, are in custody after shooting at a school near Denver.

Two students have opened fire at a Colorado science and technology school, killing a fellow student and wounding seven others before being taken into custody, law enforcement and hospital officials in the United States said.

The Douglas County Sheriff’s office said deputies heard shots coming from the Science, Technology, Engineering and Math (STEM) School in Highlands Ranch, about 40km south of Denver, when they arrived to investigate reports of gunfire.

A man who identified himself as Fernando Montoya said his 17-year-old son, a junior at STEM, was shot three times, and one of his friends was also wounded.

He said his son, who was later released from a hospital, told him one attacker walked into his classroom and opened fire with a gun and another attacker was already in the classroom.

“He said a guy pulled a pistol out of a guitar case and started to shoot,” Montoya told ABC affiliate Denver 7.

Eight students were taken to a hospital with injuries, Sheriff Tony Spurlock told reporters. Several of the students were in critical condition, he said. One of those victims, an 18-year-old male, later died of his injuries, Spurlock said a short time later. Authorities did not release the name of the student who died.

The suspects were identified only as two male students of the school, one an adult and the other under age 18, the sheriff said.

Authorities said the shooting erupted in the middle school section of the campus, which combines elementary, middle and high school students.

“Two individuals walked into the STEM school, got deep inside the school, and engaged students in two separate locations,” Spurlock said.

The shooting occurred less than a month after the 20th anniversary of the Columbine High School massacre in nearby Littleton, about eight kilometres from the STEM school. In 1999, two Columbine students killed 13 people there before committing suicide in what remains one of the deadliest school shootings in US history.

On Tuesday, law enforcement officers initially searched STEM for a possible third suspect but police later determined that the two in custody had acted alone, officials said.

‘A bit shaky’

A student who was not identified told Denver television station KUSA-TV outside the school after the shooting that the violence had left him “a bit shaky” and “scared,” but “glad that I didn’t get hurt”.

Colorado Governor Jared Polis said he was sending additional state law enforcement officials to the scene.

“We are making all of our public safety resources available to assist the Douglas County Sheriff’s Department in their effort to secure the site and evacuate the students,” Polis wrote on Twitter.

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The sheriff’s department directed parents to go to a nearby recreation centre to pick up their children.

Local television showed dozens of police and fire vehicles surrounding the school as deputies conducted a room-by-room search of the campus.

The Denver Post reported that all schools in the area were placed on a security lockdown while police and fire crews responded to the scene.

Some of the worst mass shootings in the US have occurred in Colorado. In addition to Columbine, a man opened fire at a movie theatre in Aurora, Colorado, in 2012, killing 12 people and injuring scores more.

The bloodshed in Colorado came one week to the day after a 22-year-old gunman opened fire on the Charlotte campus of the University of North Carolina, killing two people and wounding four others. The gunman was later disarmed and arrested.

The White House offered a message of condolence. “Our prayers are with the victims, family members, and all those affected by today’s shooting,” spokesman Judd Deere said.

“The White House has been in communication with state and local officials, and the president has been briefed and continues to monitor the ongoing situation.”