  We present new Gemini spectroscopical data of the Extended Emission-Line
Region of 3C~305 radio galaxy in order to achieve the final answer of the
long-standing question about the ionizing mechanism. The spectra show strong
kinematic disturbances within the most intense line-emitting region. The
relative intensities amongst the emission lines agree with the gas being
shocked during the interaction of the powerful radio jets with the ambient
medium. The emission from the recombination region acts as a very effective
cooling mechanism, which is supported by the presence of a neutral outflow.
However, the observed intensity is almost an order of magnitude lower than
expected in a pure shock model. So auto-ionizing shock models, in low-density
and low-abundance regime, are required in order to account for the observed
emission within the region. This scenario also supports the hypothesis that the
optical emitting gas and the X-ray plasma are in pressure balance.
