Douglas High School was under lockdown shortly after noon Friday after the school's resource officer received an e-mail threat of that a shooting would take place on campus.
Douglas County deputies swept the buildings and grounds with school personnel to find the source of the e-mail, according to Sgt. Tom Mezzetta.
Students were kept in their classrooms and no one was allowed in the building.
The incident came one day after a student was injured during a gang-related fight in the school commons.
"We don't know if it's in response to yesterday's altercation," Mezzetta said.
"Exactly what the note said, I don't know. It made reference that there would be a shooting at school today (Friday)," Mezzetta said.
Mezzetta said resource officer Greg Shields, a Douglas County sheriff's deputy assigned to the high school, opened the e-mail at 12:52 p.m. and alerted school and sheriff's officers.
Mezzetta said officers would remain on campus throughout the day to ensure student and staff safety.
"We'll be there to make sure everybody gets home OK," Mezzetta said.
Classes were to dismiss at 2:06 p.m.
