  We present the rest-frame ultraviolet through near infrared spectral energy
distribution for an interacting Lyman break galaxy at a redshift z=4.42, the
highest redshift merging system known with clearly resolved tidal features. The
two objects in this system - HDF-G4 and its previously unidentified companion -
are both B_{435} band dropouts, have similar V_{606}-i_{775} and
i_{775}-z_{850} colors, and are separated by 1", which at z=4.42 corresponds to
7 kpc projected nuclear separation; all indicative of an interacting system.
Fits to stellar population models indicate a stellar mass of M_\star =
2.6\times 10^{10} M_\odot, age of \tau_\star = 720 My, and exponential star
formation history with an e-folding time \tau_0 = 440 My. Using these derived
stellar populations as constraints, we model the HDF-G4 system using
hydrodynamical simulations, and find that it will likely evolve into a quasar
by z\sim3.5, and a quiescent, compact spheroid by z\sim 2.5 similar to those
observed at z > 2. And, the existence of such an object supports galaxy
formation models in which major mergers drive the high redshift buildup of
spheroids and black holes.
