We construct a model of high energy heavy ion collisions as two ultrarelativistic shock waves colliding in AdS_5. Using AdS/CFT correspondence we argue that this setup corresponds to describing a heavy ion collision at strong coupling. We argue that expansion of the energy density of the medium produced in the collision in the powers of proper time squared corresponds on the gravity side to a perturbative expansion of the metric in graviton exchanges. We point out that shock waves corresponding to physical energy-momentum tensors of the nuclei completely stop almost immediately after the collision in AdS_5, which, on the field theory side, corresponds to complete nuclear stopping due to strong coupling effects, likely leading to Landau hydrodynamics. Since in real-life heavy ion collisions the large Bjorken-x part of nuclear wave functions continues to move along the light cone trajectories of the incoming nuclei leaving the small-x partons behind, we conclude that a pure large coupling approach is not likely to adequately model nuclear collisions.