  The Swift satellite has enabled us to follow the evolution of gamma-ray burst
(GRB) fireballs from the prompt gamma-ray emission to the afterglow phase. The
early x-ray and optical data obtained by telescopes aboard the Swift satellite
show that the source for prompt gamma-ray emission, the emission that heralds
these bursts, is short lived and that its source is distinct from that of the
ensuing, long-lived afterglow. Using these data, we determine the distance of
the gamma-ray source from the center of the explosion. We find this distance to
be 1e15-1e16 cm for most bursts and we show that this is within a factor of ten
of the radius of the shock-heated circumstellar medium (CSM) producing the
x-ray photons. Furthermore, using the early gamma-ray, x-ray and optical data,
we show that the prompt gamma-ray emission cannot be produced in internal
shocks, nor can it be produced in the external shock; in a more general sense
gamma-ray generation mechanisms based on shock physics have problems explaining
the GRB data for the ten Swift bursts analyzed in this work. A magnetic field
dominated outflow model for GRBs has some attractive features, although the
evidence in its favor is inconclusive. Finally, the x-ray and optical data
allow us to provide an upper limit on the density of the CSM of about 10
protons per cubic cm at a distance of about 5e16 cm from the center of
explosion.
