The two students accused of opening fire on classmates at their Denver high school have been revealed as an 18-year-old boy and a young girl - as authorities say the 18-year-old student who was shot dead was due to graduate in just three days.
Devon Erickson, 18, and a juvenile female - who authorities previously identified as a boy - were taken into custody following the shooting at STEM School Highlands Ranch in Denver on Tuesday afternoon.
The Douglas County Sheriff's Office said they had initially believed the female shooter was a male based on appearances and were not able to confirm her gender until an interview had taken place.
The underage student is in the process of transitioning from female to male, law enforcement sources told the Denver Channel.
Kendrick Castillo, 18, was killed when the two students stormed in an opened fire on students in classrooms armed with at least two handguns.
Eight students suffered gunshot wounds in the shooting and three of them remain in intensive care in hospital. Five had been discharged from the hospital by Wednesday morning.
Authorities have not yet released a motive for the shooting.
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Devon Erickson, 18, has been identified as one of the two suspects who allegedly opened fire on STEM School Highlands Ranch in Colorado on Tuesday afternoon
Castillo, the 18-year-old student who was shot dead, was just three days away from graduating, according to Douglas County Sheriff Tony Spurlock.
Classmates said Castillo was among a group of three students who tried to take down one of the shooters by tackling them when they stormed the classroom.
Kendrick Castillo, 18, died on Tuesday afternoon when two students stormed STEM School Highlands Ranch in Denver and opened fire with at least two handguns
Douglas County Sheriff Tony Spurlock said shots were fired in two separate locations in the high school section of the campus, which serves grades kindergarten through 12th.
Administrators reported the gunfire immediately and deputies arrived on the scene within two minutes.
Spurlock said officers engaged the suspects and there was a struggle to bring them down. Neither suspect was injured in the confrontation.
Authorities recovered three handguns and a rifle but said the latter was not used in the shooting.
Before officers arrived, one heroic student, Brendan Bialy, tackled one of the gunmen.
Bialy's father told the New York Times that 'two students entered the classroom and one pulled a gun out of a guitar case'.
He said 'his son and two friends tried to tackle the gunman but one of the boys was shot in the chest', according to the Times.
That account was corroborated by the father of one of the teenagers who was shot.
Fernando Montoya told The Denver Channel his son, who was shot three times but is expected to survive, told him a shooter produced a gun from a guitar case.
Terrified students were evacuated from the school after shots were fired at 1.53pm
Fernando Montoya (left) said his son was shot three times but is expected to survive
Authorities were seen outside a home believed to be owned by Erickson's parents
Authorities were seen outside a home in Highland Springs believed to be owned by Erickson's parents, James and Stephanie. The mother's Facebook page was deleted shortly after news broke of the shooting.
A reporter for 9News, Katie Eastman, tweeted a photo of the home and wrote: 'A neighbor confirmed to me that Devon lived here in this blue house on Mountain Maple Avenue in Littleton. Called him a "great kid from a great family".'
A car spray painted with the words 'f*** society' was towed away from the house at around 10pm.
A criminal background check revealed Erickson's almost unblemished record, which noted a ticket for careless driving issued in Douglas County on February 13, 2018.
Erickson is seen playing guitar in a video shared on his YouTube channel. Witnesses reported that one of the gunmen pulled a firearm out of a guitar case
The teen's social media pages indicate that he is an avid guitar player, youth theater actor and registered Democrat who has on occasion expressed disdain for Christians, criticized President Donald Trump and praised former President Barack Obama.
In a post from 2014, Erickson wrote: 'You know what I hate? All these Christians who hate gays, yet