(JTA) — The Holocaust Center for Humanity in Seattle was vandalized with what it said was white supremacist graffiti.

The graffiti was discovered on Wednesday, the center said in a letter released the following day.

The spray-painted graffiti, described as “obscure white supremacist symbols,” was discovered as a teachers seminar was taking place, the center said. “(I)t became a teachable moment, driving home the importance and relevance of our work. It is not a history lesson – similar violations are happening every day around the world,” the letter said.

It is the first time in its 30-year history that the building has been targeted, local news station KIRO Channel 7 reported.

The Seattle Police Bias Unit is investigating.