When a Rydberg state is suddenly excited to an autoionizing Rydberg state by a short-pulse core-electron excitation, a shock wave is created in the Rydberg electron's wave function. This shock wave originates at small r, at the excited core, and propagates outward. This wave-function disturbance is best illustrated by the Rydberg wave function in momentum space, where the autoionization process can be seen as a filtering process that reduces the high-momentum, outgoing wave function.