The dynamics of the electron shock in a two-fluid plasma simulation of the planar Richtmyer-Meshkov instability of a thermal interface are presented. In this study the electron shock is generated by a general Riemann problem before processing the electron density interface. The interface then undergoes significant oscillation which is coupled to a breakdown of the electron shock into an oscillatory wave packet. The evolution of the electron fluid is shown to be heavily dominated by electromagnetic effects due to the presence of charge separation. Acceleration of the electron fluid by the Lorentz force is found to be equal in magnitude to that provided by the pressure gradient leading to the observed oscillatory behavior.