Burke County Sheriff Williams told Newsweek his office was working with state and federal authorities to determine the person responsible for the threat.
"When I read this, it didn't seem like their usual script, which is typically of poor academic quality," the school staff member who uncovered the deception wrote in an email to the superintendent.
The theme has been removed and the school district is not planning any further action, according to a spokesperson for the school district.
The new photo that the student submitted still has the American flag displayed prominently.
Rodney Lynn of Coffs Harbour Christian Community School in New South Wales, Australia, did not mention Thunberg by name but spoke of a "a little girl from Scandinavia" the very same week Thunberg addressed politicians at the United Nations General Assembly.
"She said that yes, she locked him out. That she felt she was in danger, so she wanted to make sure everyone was safe so she locked him out."
The principal sent a memo last year restricting Christmas-themed items in classrooms, stirring controversy.
The teacher racked up a bill of more than $2,100.
"I'm sick of her," Roosevelt High School principal Aqueelha James said. "I'm going to have a long, drawn-out email just so that I can embarrass her."
A Rochester, New York prep school's first black valedictorian was forbidden from speaking at his graduation for several "run-ins" with his principal. So the mayor stepped in.
"There is a rigorous acceptance process at ESA, and all students must demonstrate their artistic and academic potential from the start. Even if this were not the case, the assumption she made was that Black students and families are inherently less capable than their white and 'white-r' counterparts."
Rod Rosenstein's new acting top deputy is Edward O'Callaghan, who worked for the McCain-Palin campaign.