It's not what you think -- the shuttle didn't malfunction or anything. It actually did exactly what it was programmed to do. During a stop at an intersection, a truck in front of the shuttle started backing up, so the shuttle's sensors commanded the bus to stay still. The truck in front of the shuttle, however, never stopped, and grazed the front fender a bit.
Nothing serious, no one was hurt, just a majorly ironic hilarious situation.