  The gamma-ray burst (GRB) of October 17, 1994 (941017), showed a distinct
high energy spectral component extending from $\lesssim$ a few MeV to $\gtrsim$
200 MeV, in addition to the typical GRB emission which peaked at $\lesssim$ a
few hundred keV. The high energy component carried at least $\sim$ 3 times more
energy than the lower energy component. It displayed an almost constant flux
with a rather hard spectrum ($F_\nu \propto \nu^{-\alpha}$ with $\alpha \sim
0$) from $\lesssim$ 20 s into the burst up to $\sim$ 200 s, while the duration
of the GRB, where 90% of the energy in the lower energy component was emitted,
was only 77 s. Such a high energy component was seen in only one out of $\sim$
30 GRBs in which a similar component could have been detected, and thus appears
to be quite rare. We examine possible explanations for this high energy
spectral component and find that most models fail. The only emission region
that provides the right temporal behavior is the reverse shock that goes into
the GRB ejecta as it is decelerated by the ambient medium, or possibly the very
early forward shock while the reverse shock is still going on. The best
candidate for the emission mechanism is synchrotron self-Compton emission from
the reverse shock. Even in this model the most natural spectral slope is only
marginally consistent with the observed value, and some degree of fine tuning
is required in order to improve the agreement. This might suggest that an
additional or alternative emission mechanism is at work here. A prediction of
this interpretation is that such a high energy component should be accompanied
by a bright optical transient, similar to the one observed in GRB 990123.
