HIGHLANDS RANCH, Colo. (AP) — 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.

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.

Douglas County Sheriff Tony Spurlock told reporters that the suspects had a "number of weapons." Those weapons included two handguns which that Spurlock said the suspects were not old enough to buy or own.

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.

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 Wednesday.

Giasolli said another student lunged at the shooter, giving the other students time to dive under the desks and flee to safety.

At least one student encountered the suspects during the shooting, Sheriff Tony Spurlock said. He did not elaborate.

"We're going to hear about very heroic things that have taken place at the school," Spurlock said.

He declined to identify the student who was shot and killed at the school.

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.