A memorial in Prague commemorating the escape of hundreds of Jewish children from the Nazis has been vandalized, The Guardian reports. A long crack in the window pane of the bronze Valediction Memorial at Prague’s main railway station is reportedly said to be the result of an intentional attack. “One hundred percent, this was planned,” said Jan Hunat, the Czech engraver who designed the pane—a 18mm-thick piece of glass engraved with hands to represent the 669 children and adults waving goodbye from a train transporting them from the Czech capital to Britain in 1939. “The person who did this has definitely gone prepared to do it. The glass is 18mm thick and there’s no way it could have been broken otherwise. On one of the hands, even the tips of the fingers are broken.” The memorial, which also honors those parents who put their children on the train after the Nazis invaded Czechoslovakia, was first unveiled in 2017.