  Recent high-energy missions have allowed keeping watch over blazars in
flaring states, which provide deep insights into the engine powered by
supermassive black holes. However, having a quasar caught in a very bright
flaring state is not easy requiring long surveys. Therefore, the observation of
such flaring events represents a goldmine for theoretical studies. Such a
flaring event was captured by the INTEGRAL mission in June 2015 while
performing its (as of today) deepest extragalactic survey when it caught the
prominent blazar 3C~279 in its brightest flare ever recorded at gamma-ray
energies. The flare was simultaneously recorded by the Fermi gamma-ray mission,
by the Swift mission, by the INTEGRAL mission and by observations ranging from
UV, through optical to the near-IR bands. The derived snapshot of this broad
spectral energy distribution of the flare has been modeled in the context of a
one-zone radiation transfer leptonic and lepto-hadronic models constraining the
single emission components. The derived parameters of both models challenge the
physical conditions in the jet. However, very recently published
very-high-energy (VHE) data at TeV energies are very close to our
lepto-hadronic model.
