  We assume that internal shocks of Gamma Ray Bursts (GRBs) consist of multiple
sub-jets with a collimation half-angle $\sim {\rm several
}\times\gamma_i^{-1}$, where $\gamma_i$ is the Lorenz factor of each sub-jet.
If by chance a sub-jet is first emitted off-axis from the line of sight, the
observed peak energy can be in the X-ray region. Next if by chance a subsequent
sub-jet is emitted along the line of sight, then the peak energy will be in the
gamma ray region and the gamma ray may arrive after the X-ray precursor from
the former sub-jet depending on parameters. This model predicts a new class of
GRBs with extremely weak and short gamma ray emission but X-ray precursor
and/or post-cursor as well as an afterglow.
