Photon statistical measurements on a semiconductor microlaser, obtained using single-photon counting techniques, show that a newly discovered spontaneous pulsed emission regime possesses superthermal statistical properties. The observed spike dynamics, typical of small-scale devices, is at the origin of an unexpected discordance between the probability density function and its representation in terms of the first moments, a discordance so far unnoticed in all devices. The impact of this new dynamics is potentially large, since coincidence techniques are presently the sole capable of characterizing light emitted by nanolasers.