  It has been suggested that a non-repeating fast radio burst (FRB) represents
the final signal of a magnetized neutron star collapsing to a black hole. In
this model, a supramassive neutron star supported by rapid rotation, will
collapse to a black hole several thousand to million years after its birth as a
result of spin down. The collapse violently snaps the magnetic-field lines
anchored on the stellar surface, thus producing an electromagnetic pulse that
will propagate outwards and accelerate electrons producing a massive radio
burst, i.e. a "blitzar". We present a systematic study of the gravitational
collapse of rotating and magnetised neutron stars with special attention to
far-field evolution at late times after the collapse. By considering a series
of neutron stars with rotation ranging from zero to millisecond periods and
different magnetic-field strengths, we show that the blitzar emission is very
robust and always characterised by a series sub-millisecond pulses decaying
exponentially in amplitude. The luminosity and energy released when the
magnetosphere is destroyed are well reproduced by a simple expression in terms
of the stellar magnetic field and radius. Finally, we assess the occurrence of
pair production during a blitzar scenario, concluding that for typical
magnetic-field strengths of $10^{12}\,{\rm G}$ and spin frequencies of a few
Hz, pair production is suppressed. Overall, the very good match between the
results of the simulations and the luminosities normally observed for FRBs
lends credibility to the blitzar model as a simple and yet plausible
explanation for the phenomenology of non-repeating FRBs.
