  Deep 1.1 mm continuum observations of 1E0657-56 (the "Bullet Cluster") taken
with the millimeter-wavelength camera AzTEC on the 10-m Atacama Submillimeter
Telescope Experiment (ASTE), have revealed an extremely bright
(S$_{\rm{1.1mm}}=15.9$ mJy) unresolved source. This source, MMJ065837-5557.0,
lies close to a maximum in the density of underlying mass-distribution, towards
the larger of the two interacting clusters as traced by the weak-lensing
analysis of Clowe et al. 2006. Using optical--IR colours we argue that
MMJ065837-5557.0 lies at a redshift of $z = 2.7 \pm 0.2$. A lensing-derived
mass-model for the Bullet Cluster shows a critical-line (caustic) of
magnification within a few arcsecs of the AzTEC source, sufficient to amplify
the intrinsic millimeter-wavelength flux of the AzTEC galaxy by a factor of
$\gg 20$. After subtraction of the foreground cluster emission at 1.1mm due to
the Sunyaev-Zel'dovich effect, and correcting for the magnification, the
rest-frame FIR luminosity of MMJ065837-5557.0 is $\le 10^{12} \rm L_{\odot}$,
characteristic of a luminous infrared galaxy (LIRG). We explore various
scenarios to explain the colors, morphologies and positional offsets between
the potential optical and IR counterparts, and their relationship with
MMJ065837-5557.0. Until higher-resolution and more sensitive (sub)millimeter
observations are available, the detection of background galaxies close to the
caustics of massive lensing clusters offers the only opportunity to study this
intrinsically faint millimeter-galaxy population.
