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.
Giasolli said Castillo lunged at the gunman, who then shot the teen.
Castillo was a member of the school's robotics club called FRC 4418 Impulse.
The two teenagers are accused of opening fire on fellow students in two classrooms at the Science, Technology, Engineering and Math (STEM) School in Highlands Ranch, about 25 miles (40 km) south of Denver.
The White House also tweeted its condolences to the victims, while spokesman Judd Deere said President Donald Trump "has been briefed and continues to monitor the ongoing situation".
Another, Brendan Bialy, is a student enrolled in the U.S. Marine Corps' delayed entry program, NBC News reported. "She said 'guns, shooting, oh my god, oh my god.' And she could hear them and that's how I first knew".
Describing public reaction to the attack, Polis said, "At this point, I think Coloradans are really heartbroken, frustrated, still shocked and, frankly, sick over a mass shooting occurring right here in Douglas County".
"I have to believe that the quick response of the officers that got inside that school helped save lives", Spurlock said.
As gunfire echoed through the school, students hid or ran through the halls, some shouting.
Trump Fights Congress over Mueller Report
House Speaker Nancy Pelosi suggested Democrats were surprised by the department's decision as last-minute talks failed. The last attorney general to be held in contempt of Congress was Eric Holder in 2012 during the Obama administration.
"Two individuals walked into the STEM school, got deep inside the school, and engaged students in two separate locations", Spurlock said.
The school serves children from Kindergarten to 12th grade.
Though authorities initially said they were looking for a possible third suspect, Nicholson-Kluth said they are no longer looking for another suspect. Two suspects, both students, were taken into custody - Devon Erickson, 18, and a juvenile.
"And the next thing I know he's pulling a gun and he's telling nobody to move".
Two of the victims were in serious condition at Littleton Adventist Hospital, officials said, and three had been released from the hospital. One is an adult and the other is a juvenile.
It was unclear Wednesday if Erickson had legal representation ahead of an initial hearing in his case, which will happen later today.
He explained that his daughters, who do not attend the school where the shooting took place, have been on lockout at their school twice in the last month.
Sophia Marks' mother, Sara Marks, said she has two other children who also go to the school.
Authorities say the two students accused of killing a classmate in a shooting at a school in suburban Denver used at least two handguns in the attack.