Two high school students shot and killed a classmate and injured eight others at a charter school in a Colorado community, US that just weeks ago marked the 20th anniversary of one of the nation’s worst school shootings.

Douglas County sheriff’s officials said Devon Erickson, 18, and a younger student walked into the STEM School Highlands Ranch through an entrance without metal detectors and opened fire with two handguns on students in two classrooms.

As gunfire echoed through the school, students hid others ran through the halls, some shouting.

Commenting on the incident, Seventh grader Sophia Marks said she did not know what was happening as she on,y saw flashes and heard bangs.

“No one really knew what was going on so I didn’t know they were bullets,” said Sophia. “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.

Currently the two are in custody outside Denver, accused of opening fire in a charter school, killing a teenager and wounding eight others. Authorities say the student who was killed was an 18-year-old male.