  We compare the ongoing observations of the remarkable burst GRB990123, the
mother of all bursts, with the predictions of the afterglow theory. We show
that the observations agree with the recent prediction that a reverse shock
propagating into the ejecta would produce a very strong prompt optical flash.
This reverse shock has also produced the 8.46GHz radio signal, observed after
one day. The forward shock, which propagates into the ISM is the origin of the
classical afterglow. It has produced the prompt X-ray signal as well as the
late optical and IR emission. It would most likely produce a radio emission
within the next few weeks. The observations suggest that the initial Lorentz
factor of the ejecta was $\sim 200$. Within factors of order unity, this crude
model explains all current observations of GRB990123.
