A mechanism to explain the existence of two distinctly different kinds of energetic electron bursts within the Hermean magnetosphere is presented. The spectrally-soft, very intense increases of energetic electrons observed in situ by Mariner 10 are ascribed to ''substorm-like'' dissipation events due to magnetic reconnection in Mercury's magnetosphere, characterized by lower peak intensities and much harder energy spectra, are attributed to Jovian electrons which first enter and are subsequently confined in the Herman system. This Jovian electron model at Mercury is closely analogous to a similar model of such Jovian electron effects within the terrestrial magnetosphere to produce highly relativistic electron bursts by internal generation mechanisms.