  We consider the morphology, stellar populations, structure and AGN activity
of 10 post-starburst (K+A) galaxies with HST observations, full spectral
coverage in the optical, spectral energy distributions from 0.2 to 160 $\mu$m,
X-ray and radio data. Our results show that the PSG phenomenon is related to
mergers and interactions, and that star formation was likely triggered during
close passes prior to final coalescence. We performed a detailed qualitative
analysis of the observed light distribution, including low-surface brightness
tidal features and color profiles, in high-resolution multi-band imaging with
HST. We find evidence that star formation was centrally concentrated and that
quenching took place from the inside-out, consistent with the occurrence of a
feedback episode. Most of our PSGs contain massive bulges and therefore should
host supermassive black holes. We search for AGN activity in spectra (line
ratios), optical variability, X-ray emission at 0.5--7.0 KeV and radio emission
at 20cm: all four lines of evidence show there is no active AGN accreting at
more than 0.1\% of the Eddington luminosity. We conclude that mergers may be a
necessary, but not a sufficient condition, for AGN activity and that they are
not likely to be important in our objects. If PSGs are good test cases for
quenching and evolution to the red sequence, AGNs may play a smaller role than
expected.
