On the same day students at more than 3,000 schools across the country walked out of their classrooms to protest gun violence, Morgan Roof—the sister of convicted mass shooter Dylann Roof—was arrested for bringing a knife and pepper spray into her South Carolina high school, CNN reports.

The 18-year-old also wrote what her school's principal called an "extremely inappropriate" and "hateful" message on Snapchat, which surfaced on Twitter Wednesday.

"I hope it's a trap and y'all get shot," Roof wrote of the walkout, a memorial for the 17 people killed in last month's school shooting in Parkland, Florida. "We know it's fixing to be nothing but black people walkin out anyway."

Roof's brother, Dylann, was sentenced to death last year for gunning down nine black parishioners at a church in South Carolina, a crime for which the self-identified white supremacist showed no remorse.

A resource officer found the knife and pepper spray on Morgan Roof at school, along with a small amount of weed, according to CNN. She was charged with simple possession of marijuana and two counts of carrying weapons on school grounds, and a judge set her bond at $5,000, local NBC affiliate WIS reports. She's also been ordered to stay away from school grounds.

It wasn't the first scare at Roof's high school this week: According to the Post and Courier, two students were arrested Tuesday for bringing a handgun and ammunition to A.C. Flora High School, though the incident was reportedly unrelated.

In response to the arrests of Roof and the other two students, South Carolina Governor Henry McMaster wrote on Twitter that "potential tragedy was avoided" at the school. A.C. Flora's principal Susan Childs sent a letter to parents letting them know that the incidents had been handled.

"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," Childs wrote. "Be assured that the safety of our students will always be our top priority."

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