The documents were published by the North Carolina Information Sharing and Analysis Center (NC ISAAC). The bulletin said the called were all investigated and determined to be April Fools' hoaxes.
In each call, the caller claimed to be hiding from a shooter somewhere in the school. In each instance, that turned out to be a fabrication.
"It is likely the calls are being made as part of a larger April Fools' Day prank and more calls could continue throughout the day," the bulletin read.
One such instance happened Monday morning at Apex High School.
The school went on lockdown for about 15 minutes while School Resource Officers investigated.
According to the ABC affiliate in Charlotte, Kings Mountain High School, East Lincoln High School, Crest High School, Freedom High School and South Caldwell High School all had reports of active shooters -- even though some of those schools were out of session for spring break.