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 = 2.6times 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 zsim3.5, and a quiescent, compact spheroid by zsim 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.
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