A swastika was found attached to a bathroom wall in a downtown D.C. high school Monday, administrators said, two days after an attack at a Pittsburgh synagogue took 11 lives.

The principal at School Without Walls — a selective application public high school — said in a letter to parents that administrators immediately removed the anti-Semitic sticker.

“I wanted to inform you of this incident and assure you that acts of hate will not be tolerated,” the school’s principal, Richard Trogisch, wrote in an email to parents Tuesday.“At School Without Walls, we remain committed to ensuring that our campus is a safe space for learning and achievement for all students regardless of race or religion.”

D.C. police said they are investigating.

The gunman who burst into Tree of Life synagogue in Pittsburgh yelled anti-Semitic insults.

The shooting has intensified conversations about anti-Semitism throughout the country.

In March 2017, administrators at School Without Walls investigated an incident involving a swastika drawn on the wall of a boy’s restroom. At the time, an administrator said security officials reviewed the school’s cameras to determine who went into the bathroom, but the tape showed too many students to identify a perpetrator.

In September 2017, authorities investigated a swastika found painted inside a residence hall restroom at Georgetown University at the start of Rosh Hashanah, the Jewish New Year.

Other symbols of hate have appeared on D.C.-area campuses in recent years. In September 2017, Confederate flag posters bearing chunks of cotton were discovered at American University. The posters appeared just months after another racially charged incident on AU’s campus, involving bananas found hanging from strings in the shape of nooses.