A gray concrete slab with a window through which viewers can watch a video of two men kissing served as memorial to the thousands of gays persecuted and tortured by the Nazis. The monument has been vandalized for the second time in only four months, reports The Associated Press.

According to the report, Berlin police say someone broke the window that allows visitors to peer into the monument and watch the video.

In August, vandals also broke the window and damaged a nearby fence.

The monument sits in the center of Berlin, along the Tiergarten Park across from the much larger memorial to Jewish victims of the Holocaust.

Estimates claim that up to 50,000 gays were labeled criminals and outcasts by Germany's Nazi party after Hitler outlawed homosexuality in 1936, calling it “unnatural” behavior unbecoming of the Aryan “master race.” As many as 15,000 gays were tortured and died of hunger, disease, or abuse in Nazi concentration camps, where they were identified with a pink triangle.

Openly gay Berlin Mayor Klaus Wowereit and about 100 protesters staged a protest after the first attack to denounce homophobia.

Homophobia had kept the German government from officially recognizing the Nazi's homosexual victims until last year, when the German Parliament agreed to pay $1 million dollars to fund the memorial.

The memorial was inaugurated in May.