UPDATE: Two Students Opened Fire On Their Colorado School, Killing One Classmate And Injuring At Least Seven Others

"I'm like, what ... is this real or fake?" a sixth-grader recalled. "I just ran after them. ... I just got out of there."

Two students opened fire inside a Colorado school Tuesday, killing one classmate and injuring seven others, authorities said.

Administrators at STEM School, a K-12 charter in the Denver suburb of Highlands Ranch, reported hearing gunshots fired at 1:53 p.m. Deputies from the Douglas County Sheriff's Office arrived on the scene two minutes later and engaged two suspects.

Sheriff Tony Spurlock said the suspects, one adult man and one juvenile boy, were taken into custody. Both are students at the school, and officials do not believe there were any additional suspects.

"We know that two individuals walked into the STEM School, got deep inside the school, and engaged students in two separate locations," Spurlock told reporters. "There were a number of students that were shot and injured."

Eight victims, aged 15 and older, were being treated in local hospitals. No employees or teachers were injured in the shooting, Spurlock said.

The sheriff's office said Tuesday night that one of the victims, an 18-year-old male student who was not immediately identified, had died.

Littleton Adventist Hospital received five patients, a spokesperson confirmed to BuzzFeed News. As of Tuesday afternoon, two were listed in serious condition. The three others have been discharged from the hospital.

Linda Watson, a spokesperson for Sky Ridge Medical Center in Lone Tree, Colorado, said the hospital was treating two juvenile victims. Both were in stable condition. Children's Hospital of Colorado was treating one patient who was in good condition at its south campus in Highlands Ranch.

"Quite a few shots were fired and police officers, sheriff's officers were on scene almost immediately," Douglas County Undersheriff Holly Nicholson-Kluth told reporters, adding that deputies could still hear gunshots as they arrived on scene and entered the school.

Spurlock said he believed the deputies' quick response to the shooting saved lives.

"I want to think that that is something that helped," he said.

The school does not have a resource police officer assigned to the campus, but does have private security, Spurlock said.

He declined to provide additional information about the suspects but said they were not on the sheriff's department's radar. Officials were working to obtain search warrants to search a suspect's vehicle and the suspects' homes, he said.

A motive for the shooting has not been determined, and Spurlock said officials did not have any information about anyone being specifically targeted at the school.

The FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives in Denver were assisting in the investigation.

The White House said President Donald Trump has been briefed on the shooting and is monitoring the situation.

"Tragically, this community and those surrounding it know all too well these hateful and horrible acts of violence," Judd Deere, the White House deputy press secretary, said in a statement. "We offer our full support to local law enforcement and first responders and thank them for their heroism."

The school was placed on lockdown for several hours, according to the Douglas County School District. All other Highlands Ranch schools were placed on lockout.

More than 1,800 students in elementary, middle, and high school attend STEM School, according to its website.

Nicholson-Kluth said many students self-evacuated after the shooting began. Parents were being reunited with students at Northridge Recreation Center.

Students are escorted to a school bus in front of STEM School Highlands Ranch after the shooting.

Speaking on air to the Denver ABC affiliate, Christian, a sixth-grader, said he was in study hall when he saw several students running and yelling, "School shooter, school shooter!"

"I'm like, what ... is this real or fake?" he said. "I just ran after them. ... I just got out of there."

Rocco DeChalk, who lives down the street from the Highlands Ranch school, said he was working from home when he looked out his window and saw crowds of kids running down the street.

"At first I thought it was a gym class," DeChalk, 50, told BuzzFeed News.

But then he saw the kids' faces. They looked nervous and scared.

When he stepped out onto his patio, a neighbor told him there had been a shooting at the school and alerted him to a young man who was sitting in the grass by his mailbox and appeared to have been shot.

DeChalk said he and the boy's friend helped him into his house.

He said the boy, who he guessed was between 12 and 15 years old, was conscious and able to walk. He had one gunshot wound in his back near his armpit.

"He was having a hard time breathing, so I didn't ask him any questions," DeChalk said.

He then waved down a police officer outside who summoned an ambulance to transport the boy to a hospital.

"It's just unbelievably scary," DeChalk said.

Parents gather in a circle to pray at a recreation center where students were reunited with their parents.

David Zalubowski / AP

The school is located less than 8 miles away from Columbine High School, where 13 people were killed by two students on April 20, 1999. The shooting was, at the time, the deadliest in the nation's history.

Colorado Gov. Jared Polis said he was monitoring the situation and making all public safety resources available to assist the sheriff's department.

"The heart of all Colorado is with the victims and their families," Polis said on Twitter.

Source: Stephanie K. Baer (BuzzFeed News)