Douglas County Coroner Jill Romann has not officially identified the deceased student, according to Douglas County Sheriff's Office.
"It's not just Highlands Ranch".
Deputies say that two shooters opened fire at STEM School Highlands Ranch in Colorado on Tuesday, leaving eight injured and one student dead. But they revised that account Wednesday, saying they have identified the juvenile suspect as a female.
The school will be closed the rest of the week.
Witnesses said that Castillo "lunged" at a suspect, saving others.
His accused accomplice, who is under the age of 18 and has not been publicly identified, is being charged separately as a juvenile, authorities said.
At least one student encountered the suspects during the shooting, Sheriff Tony Spurlock said.
"A student's life was taken too soon by this act of violence", Colorado Gov. Jared Polis said at a news conference. The condition of the boy shot was not known.
"We've had instances where immediately afterwards, we've had staff that just can't continue their shift and we support them and allow them to leave depending on what that situation was", Elliott said.
"Thank God he is fine", Montoya said. "Even though I was inches away, I didn't get shot". He's going to walk out on his feet, so I'm glad.
"This is every parent's worst nightmare and it's something that when you see your kids go to school in the morning, it's "Have a great day" and just assume everything is going to be all right". Authorities are in the early stages of interviewing witnesses and learning what happened, the sheriff said. "They completely and utterly failed in a matter of half a minute", he said of the attackers.
More than 1,850 students attend the STEM school, which includes grades K-12, according to its website.
One student at the school told CBS News Mr Erickson had talked about inflicting harm and sadness.
"Our STEM family is hurting tonight".
- Holly Nicholson-Kluth, Undersheriff - Douglas County Sheriff's dept. "Supporting one another in the coming days, weeks and months is critical". "Never said a mean joke".
The FBI is investigating the crime scene, Spurlock said. He said he knew both suspects, including one who was in his graduating class, but he only saw one of the suspects in his classroom.
He did not release additional information on the suspects.