How did Gleaming The Cube get a skateboard to break a pane of glass?

One of the cooler stunts in the 1989 skateboarding movie Gleaming The Cube happens at the climax of the film, when Brian, played by tousle-haired Christian Slater, crashes through a glass window in a misguided attempt at heroics. In the video above, production designer John Muto explains how they pulled off the high-flying stunt.