We present a dark matter model to explain the excess events in the electron recoil data recently reported by the Xenon1T experiment. In our model, dark matter $\chi$ annihilates into a pair of on-shell particles $\chi$ , which subsequently decay into the $\chi$ final state; $\chi$ interacts with electrons to generate the observed excess events. Because of the mass hierarchy, the velocity of $\chi$ can be rather large and can have an extended distribution, providing a good fit to the electron recoil energy spectrum. We estimate the flux of $\chi$ from dark matter annihilations in the galaxy and further determine the interaction cross section, which is sizable but sufficiently small to allow $\chi$ to penetrate the rocks to reach the underground labs.