Burke County Sheriff Williams told Newsweek his office was working with state and federal authorities to determine the person responsible for the threat.
Former Newtown superintendent Dr. Joe Erardi told Newsweek he expected "this upcoming school year was going to be the most violent return that America has ever seen."
Lt. Benjamin Blick said that it didn't appear to be a "traditional" active shooter situation since authorities haven't determined whether the shooter or shooters were firing at anyone.
Police rushed to a factory in Springfield, Ohio, after one worker texted her sister to say she was hiding from an active shooter on site.
Sheriff's deputies and firefighters responded to a "possible shooting" today next to the Jacksonville International Airport.
"My son's school is holding 4 active shooter drills this year. The only clear impact of these drills is stress, anxiety and confusion on the part of children and families. I would end the drills or make them optional. Let our kids learn the right things," Yang tweeted Monday.
Oakland University said using the discs is a last resort but could still cause "quite the distraction."
Local police responded to reports of an active shooter in the community of Hampstead, North Carolina.
"There have been 22 school shootings in the U.S. since the beginning of this year. Why would anybody think it's a good idea?"
Santa Fe Police said officers are on the scene at the high school.
After the Parkland, Florida, school shooting, school violence incidents have increased dramatically.
The massacre is the worst in Texas's history.
As mass shootings become more common, the FBI has endorsed a training program for first responders—one that recommends civilians keep their guns holstered.