Hundreds of high-school students, some chanting "Black Lives Matter," walked out of school in Berkeley, California, on Thursday and marched to a nearby campus to protest a threatening and racist message left on a school computer, police said, according to Reuters. As many as 1,000 Berkeley High School students left class around 10 a.m. (1800 GMT), after school district officials had notified parents the night before about the hateful message, said Berkeley Police Department spokesman Byron White. The message, shared on Twitter by the school's black student union and then published by local news outlets, included racial slurs, a claim of past racial violence, a reference to the Ku Klux Klan, and threatened a "public lynching" in December. "It's definitely hateful. We're looking into this as a hate crime," White said, adding the incident was under investigation. The students assembled outside the high school and marched a few blocks to the campus of University of California Berkeley, chanting and carrying signs. Among the chants was "Black Lives Matter," a refrain that has come to define a national movement against systemic racism and police violence that spawned last year in the wake of numerous high-profile police killings of unarmed black men. White said there were no reports of arrests or injuries and that the protest was peaceful. He said police were monitoring the event and blocking off streets to allow students to march. The black student union called the message "terrorism" in a statement and demanded immediate action. "The safety of Black students has been explicitly threatened," the statement said. Berkeley High senior Navya Laki, 17, said the union went class to class to spread word of the protest. She said a previous racial incident on campus had not been taken seriously by staff, and said: "With this one, it's like we were fed up. We are going to do something about it." District officials told the local San Francisco Chronicle newspaper that the image seemed to be a screen shot of the school's library home page which had been modified to include the racist language. Officials told the newspaper they did not believe someone hacked into the school's system, nor did they think the web site had been altered. The district could not be immediately reached for comment.