Two high school students used at least two handguns in the shooting at a charter school that killed one of their classmates and injured eight others in a Colorado community that just weeks ago marked the 20th anniversary of one of the nation's worst school shootings, authorities said Wednesday.
The shooting's lone fatality was Kendrick Castillo, a friendly 18-year-old who leaped from his desk in a literature class and charged the two attackers, sacrificing his life to buy classmates time to escape.
Distraught dad John Castillo told NBC News he can't fathom how life will go on without his teenage son.
"I don’t know what I’m going to do without him in our lives," John Castillo said. "It’s never going to be the same."
He added: “I don’t know why this happened to such a good kid."
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 1999 Columbine High School 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.
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.
That Tuesday afternoon's attack at STEM School Highlands Ranch happened just miles from Columbine High School was sure to raise questions about whether it was inspired by the 1999 massacre, but the answer was not immediately clear.
Douglas County sheriff's officials said Devon Erickson, 18, and a younger student who is a juvenile and was not identified walked into the STEM School Highlands Ranch through an entrance without metal detectors and opened fire on students in two classrooms.
Spurlock told reporters that the suspects had a "number of weapons." They included two handguns that Spurlock said the suspects were not old enough to buy or own.
He also told reporters that the juvenile suspect is a girl, but an attorney for the suspect said the juvenile uses male pronouns. NBC News is not identifying the underage suspect, who has not yet been charged.
As gunfire echoed through the school, students hid or ran through the halls, some shouting.
"No one really knew what was going on so I didn't know they were bullets," said seventh-grader Sophia Marks. "I just kind of saw like flashes and we heard bangs."
Student Nui Giasolli told NBC's "Today" show she was in her British Literature class when Erickson came in late.
"He walked to the other side of the classroom where we also had another door, and he opened the door. He walked back as if he was going to go back to his seat, then he walked back to the door and he closed it. The next thing I know he's pulling a gun and he's telling nobody to move," she said.
Within minutes, deputies at a nearby sheriff's department substation entered the school and arrested the two suspects without exchanging gunfire. One of the suspects was detained by the school's security guard, Spurlock 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, bowing his head during much of the proceedings with his dark hair streaked with purple covering his eyes.
The 18-year-old nodded frequently in answering the judge's questions but at one point the judge requested a verbal answer to whether he had any questions. He simply replied, "No."
Josh Dutton, 18, told The Associated Press that he was close friends with Erickson in middle school but hadn't seen him for four years as he went to 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, a hat and sunglasses, was significantly skinnier and didn't seem interested in talking. "He said he'd just turned 18 and he owned rifles," Dutton said.
A message left at a phone number listed for Erickson's home was not immediately returned.
It was not immediately clear when the younger suspect, who has not been identified, would appear in court.
The shooting took place exactly a week after a gunman killed two students and wounded four at the University of North Carolina-Charlotte. It also comes nearly three weeks after neighboring Littleton marked the grim 20th anniversary of the Columbine school massacre that killed 13 people. The two schools are separated by about 7 miles in adjacent communities south of Denver.
"Tragically, this community and those surrounding it know all too well these hateful and horrible acts of violence," White House spokesman Judd Deere said in a statement. President Donald Trump had been briefed on the shooting and was in touch with state and local officials, Deere said.
"The heart of all Colorado is with the victims and their families," Gov. Jared Polis said in a statement.
STEM is a public charter school with a focus on science, technology, engineering and math. It has more than 1,850 students in kindergarten through 12th grade.
As the gunfire rang out, students ran through the halls shouting "School shooter!" Some wondered at first if it was a joke or a drill.
Chris Elledge, 15, said his teacher told the class to hide behind weight equipment in the room, where they stayed until police arrived.
"They busted in the room, and they were asking if there was any suspects in the room, if we were OK, and they escorted us out to go out to the front of the building," Elledge said.
Frantic parents used their cellphones to find their children as news of the shooting spread. Sophia Marks' mother, Sara Marks, said she has two other children who also go to the school.
"When you have no idea what's going on and the children are texting you that they're hiding under a desk and bullets are hitting their window, or things are hitting their window, it's a horrible feeling," she said.
Three hospitals reported treating eight people in connection with the attack. Five had been released by Wednesday morning but three remained hospitalized in intensive care, Spurlock said.
Fernando Montoya told television station KMGH that his 17-year-old son was shot three times but was expected to make a full recovery.
"Thank God he is fine," Montoya said. "Even though he got shot, he's OK. He's going to walk out on his feet, so I'm glad. We're so lucky."
Associated Press writer Nicholas Riccardi in Denver contributed to this report.