  We report on a microwave Hanbury-Brown Twiss experiment probing the
statistics of GHz photons emitted by a tunnel junction in the shot noise regime
at low temperature. By measuring the crosscorrelated fluctuations of the
occupation numbers of the photon modes of both detection branches we show that,
while the statistics of electrons is Poissonian, the photons obey chaotic
statistics. This is observed even for low photon occupation number when the
voltage across the junction is close to $h\nu/e$.
