A black teenager was arrested and charged with threatening students at Arundel High School in the Annapolis suburb of Gambrills, Maryland.
The 14-year-old female is a student at the school.
Police say she admitted creating @KoolkidsKlanKkk and @kkkforeal Twitter accounts to send racist threats, including a tweet that read, "We're planning to attack tomorrow".
Police worked with Twitter to identify the IP address of the Twitter user.
Authorities interviewed the girl in the presence of her parents, and police say she admitted to creating the Twitter account and sending the threatening tweet.
She was charged with disruption of school activities and released to her parents.
Superintendent George Arlotto issued a statement praising police officers and county leaders.
"The anonymity of the internet provides a murky and complex disguise for many who want to threaten the safety and security of our communities," he said. "Our partners in the Police Department and county government peeled back that disguise quickly in this case, in the process reassuring parents, students, and staff that our schools are safe places in which to educate our children."