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HIGHLANDS RANCH, Colo. — The lone fatality in the Colorado high school shooting was Kendrick Castillo, a friendly 18-year-old who, witnesses said, leaped from his desk in a literature class and charged the two attackers, sacrificing his life to buy classmates time to escape.

Another 18-year-old who was preparing to enter the Marines also tackled at least one of the shooters. And an armed security guard then confronted and detained one of the gunmen, officials said.

Authorities said these acts of bravery helped minimize the bloodshed from the attack, which also wounded eight people.

“We’re going to hear about very heroic things that have taken place at the school,” Douglas County Sheriff Tony Spurlock said Wednesday.

The attackers were identified by law enforcement officials as 18-year-old Devon Erickson and a younger student who is a juvenile and was not named. They allegedly walked into the STEM School Highlands Ranch through an entrance without metal detectors and opened fire in two classrooms.

Authorities on Tuesday identified the juvenile suspect as a boy but Spurlock on Wednesday told reporters that the juvenile suspect is a girl. He says “we originally thought the juvenile was a male by appearance.”

Spurlock declined comment when asked by reporters if the juvenile suspect is transgender.

KMGH-TV reported late Tuesday that the juvenile suspect is a transgender male in the process of transitioning from female to male. The television station cited anonymous sources close to the investigation.

Because the attack happened only miles from Columbine and just weeks after the shooting’s 20th anniversary, questions quickly arose about whether it was inspired by the 1999 massacre. But investigators offered no immediate motive.

Student Nui Giasolli told NBC’s “Today” show that she was in her British literature class when Erickson came in late and pulled out a gun.

Castillo lunged at the gunman, who shot the teen. Castillo’s swift action gave the rest of the class time to get underneath their desks and then run across the room to escape, Giasolli said.

A member of the school’s robotics club and a relentless tinkerer, Castillo had an infectious smile and gentle sense of humor, according to friends. He worked part-time at a local manufacturing company that had offered him a job after an internship because he was such a standout employee.

“To find he went down as a hero, I’m not surprised. That’s exactly who Kendrick was,” said Rachel Short, president of the company, Baccara.

Cecilia Bedard, 19, had known Castillo since elementary school and said he was always friendly, modest and excited to help people. He made a point of always joining his father at Knights of Columbus fundraisers and bingo nights.

“He was amazing,” Bedard said. “He was honestly the sweetest kid I ever met. Never said a mean joke.”

Brendan Bialy, also 18 and a senior who was enrolled in a delayed-entry program for the Marines, charged the shooters as well, helping fight them off, according to authorities and witnesses. “His decisive actions resulted in the safety and protection of his teachers and fellow classmates,” Marine Capt. Michael Maggiti said.

Then, as the shooters moved through the 1,800-student campus, an armed security guard detained one of them, Spurlock said.

The guard was employed by Boss High Level Protection, a company started by a former SWAT team leader who responded to the Columbine shooting. The owner, Grant Whitus, told The Associated Press the security guard is a former Marine who ran to the area of the shootings and confronted one of the armed students in a hallway.

The guard drew his weapon and apprehended the person, Whitus said.

“He doesn’t even realize how many lives he saved by stopping a school shooting,” Whitus said.

Both suspects were students at the school, and they were not previously known to authorities, Spurlock said.

Erickson made his first court appearance Wednesday and kept his head down. His black hair, streaked with purple dye, covered his face. The juvenile second attacker was due to appear before the judge immediately afterward. Formal charges were expected to be filed by Friday.

A message left at a phone number listed for Erickson’s home was not immediately returned.

Josh Dutton, 18, said he was close friends with Erickson in middle school but had not seen him for four years while attending a different high school. On Sunday, he spotted Erickson at a local light rail station and said he was shocked at how much his friend had changed.

Erickson wore all black and was significantly thinner and did not seem interested in talking.

“He said he’d just turned 18 and he owned rifles,” Dutton said.

The shooting took place exactly a week after a gunman killed two students and wounded four at the University of North Carolina-Charlotte. In that case as well, one of the fatalities was a student who charged the attacker.

The Colorado attack unfolded came nearly three weeks after neighboring Littleton marked the anniversary of the Columbine attack that killed 13 people. The two schools are separated by about seven miles in adjacent communities south of Denver.

Douglas County District Attorney George Brauchler said the community remains resilient in the face of multiple shootings, including Columbine, the 2012 theater shooting in the Denver suburb of Aurora and the 2013 shooting at Arapahoe High School.

The attacks are “aberrant acts” although they might seem otherwise to the rest of the world, he said.

“Who we are is a kind, compassionate, caring people, and this does not define us. It won’t today and it won’t tomorrow,” he said.

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