A student was killed and eight more wounded in a shooting Tuesday at a K-12 charter school south of Denver, the Douglas County Sheriff's Office reported.

The student slain was an 18-year-old man, and several of the other injured students were in critical condition after the shootings at STEM School Highlands Ranch, Sheriff Tony Spurlock said.

Devon Erickson, 18, and a boy, both students at STEM, were arrested in the shootings, Spurlock said. They "got deep inside the school and engaged students in two separate locations," he said.

He declined to identify the younger suspect but said, "We did not have them on any radar that we know of."

About two minutes after the shooting was reported at 1:53 p.m., the first deputies arrived and "engaged the suspects," he said. "I have to believe that the quick response of the officers that got inside that school helped save lives."

At 2:04 p.m., the Sheriff's Office tweeted about an "unstable situation" at the school at 8773 S. Ridgeline Blvd. and asked people to avoid the area.

A suspect vehicle was "being contained in the parking lot," and authorities were working to get search warrants for the vehicle and the suspects' houses, Spurlock said.

"We do know that we do not have any other suspects. We have all the people that are involved. So we're slowing everything down, and we're going to try to focus on processing that crime scene, taking care of those who are injured and investigating this case ... " he said.

Diego Palmer, 13, told The Denver Post he was in study hall in the cafeteria when students ran through the door yelling, "School shooting! School shooting! Get out now!" He said he wasn't sure it was real but didn't want to risk it, so he ran outside with other students to a nearby brewery, where his mother picked him up.

"It was so scary," he told The Post.

The shooting happened less than 10 miles from Columbine High School in Jefferson County, where 12 students and a teacher were gunned down April 20, 1999. More than 20 others were wounded, and the two gunmen died of self-inflicted gunshot wounds.

Just days before the 20-year anniversary of that massacre, an 18-year-old woman from Miami flew to Denver, bought a shotgun and allegedly threatened Denver-area schools, sparking panic. She was found dead of a self-inflicted gunshot wound in Clear Creek County after a nearly 24-hour manhunt.

Colorado has seen three other school shootings since Columbine, The Denver Post reported:

• A male student armed with a machete, three Molotov cocktails, a pump-action shotgun and more than 125 rounds of ammunition entered Arapahoe High School in Centennial on Dec. 13, 2013, apparently intending to intending to track down a librarian who had disciplined him. Instead, he killed a fellow student before setting fire to the library and turning the gun on himself.

• Two eighth-grade students were wounded by a gunman Feb. 23, 2010, in the parking lot of Deer Creek Middle School in Littleton. The suspected shooter was found not guilty by reason of insanity and sent to the Colorado Mental Health Institute in Pueblo.

• A teenage girl was killed at Platte Canyon High School in Bailey on Sept. 27, 2006. A gunman took her and other female students hostage and sexually assaulted them. The gunman died of a self-inflicted gunshot.

STEM School parents were asked Tuesday to go to Northridge Recreation Center, 8800 S. Broadway in Highlands Ranch, to reunite with their children after the shootings.

"We know that there are 1,800 kids that go to that school, and we are frantically trying to identify every one of those and making sure that we can connect them to their parents," Spurlock said. "That's going to take a little bit of time."

Preeti Grover told The Post that her 12-year-old son, Vivaan Kalura, sent her three alarming texts at 1:59 p.m.

"THERE IS A SHOOTING AT SHOOL (sic)."

"IM FING SCARED."

"TWO KIDS HAVE BEEN SHOT."

At first, she told The Post, she thought he was referring to a shooting at a different school. But then the messages continued.

"IM CRYING. I SWEAR TO GOD THIS IS NO JOKE."

Vivaan was in his math classroom when he heard a thud, then two gunshots in what seemed to be the next classroom over, The Post reported. He and his classmates huddled under tables in the back of the room, as his teacher told them to stay calm.

Police came to escort the children out, and Vivaan said they were told to keep their hands on their heads and walked past blood in the hallway, The Post reported. After receiving the texts, Grover raced to the school, where her 8-year-old son also is a student, then joined hundreds of parents at the recreation center.

The STEM School was placed on lockdown, meaning no one could enter or leave. And other Douglas County School District schools temporarily were placed on lockout, so no one could enter, "due to law enforcement activity in the area," the district said in a statement. All after-school activities and programs were canceled.

"Highlands Ranch families, most of our buses are being used to transport STEM students," the district tweeted at 4:08 p.m. "If at all possible, please pick up your students from other HR schools as we do not know when we will be able to get buses out to those schools."

Gov. Jared Polis tweeted: "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. We are monitoring the situation in real time. The heart of all Colorado is with the victims & their families."

The "innovative, free, public, charter learning community" has more than 1,850 students, its website says — 550 in elementary school, 700 in middle school and 600 in high school.

The school has private security but no school resource officer, Spurlock said.

Ellie is a general assignment reporter. She's a proud Midwesterner, stationery hoarder and Earl Grey tea enthusiast. After interning at The Gazette in 2015, she joined the newspaper's staff in 2016.

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