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CHICAGO, IL - APRIL 20: A student holds up her hands while taking part in National School Walkout Day to protest school violence on April 20, 2018 in Chicago, Illinois. Students from around the nation joined in the walkout against gun violence on the 19th anniversary of the shooting at Columbine High School where 13 people were killed. (Photo by Jim Young/Getty Images)
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CHICAGO, IL - APRIL 20: A student holds up her hands while taking part in National School Walkout Day to protest school violence on April 20, 2018 in Chicago, Illinois. Students from around the nation joined in the walkout against gun violence on the 19th anniversary of the shooting at Columbine High School where 13 people were killed. (Photo by Jim Young/Getty Images)
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(CNN) —  

The sister of Charleston church shooter Dylann Roof was arrested Wednesday on charges of bringing weapons and drugs to her South Carolina high school, authorities said.

Morgan Roof, 18, was arrested after a school resource officer at the A.C. Flora High School in Columbia, South Carolina was notified that Roof was carrying marijuana, pepper spray and a knife on campus, the Richland County Sheriff’s Department said.

Roof had also made an alarming Snapchat post expressing anger about the National School Walkout, The Post and Courier reported. A 17-minute walkout was staged at schools around the country on Wednesday to honor the 17 people killed at Florida’s Marjory Stoneman Douglas High School last month and call for stricter gun control laws.

No A.C. Flora High students were harmed Wednesday, authorities said.

Roof was charged with simple possession of marijuana and two counts of carrying weapons on school grounds. A judge set a $5,000 bond for Roof under the condition that she would not return to the school, CNN affiliate WIS reported.

It’s unclear whether she has an attorney.

In a letter to parents, the high school principal addressed multiple incidents that took place Tuesday and Wednesday on campus, including the one involving Roof.

“I realize that rumors and the tragic school shootings in Florida are events that can cause anxiety for our students, parents, faculty, and the community,” Principal Susan Childs wrote. “Be assured that the safety of our students will always be our top priority. We must continue to work together to maintain a safe and positive learning environment.”

South Carolina Governor Henry McMaster said “potential tragedy was avoided” Wednesday thanks to the students and educators who reported “suspicious activity” to a school resource officer.

“We owe a debt of gratitude to all involved who acted so quickly and decisively,” McMaster said in a statement.

“For months, I have called on the General Assembly to join me in placing a trained, certified police officer in every school, in every county, all day, every day,” the governor added.

Roof’s brother, Dylann, was formally sentenced to death last year for killing nine people at a historically black church in Charleston, South Carolina in 2015.

CNN’s Nicole Williams contributed to this report.