Three-dimensional solutions to the time-dependent Schrodinger equation, corresponding to the decay of resonances in the HCO radical, are studied. Theoretical tools to facilitate such studies are discussed. A novel propagation scheme, based on iterative equation equivalents to the Schrodinger equation, is developed. The HCO calculations are performed by representing the wave function with a grid and basis set expansion, and by using a Lanczos procedure to evaluate operator actions. Resonance energies and decay widths are obtained by analyzing correlation functions over relatively short time periods with Prony's method of spectral analysis. Product distributions are also estimated, and results are compared with previous time-independent scattering results. Inspection of the time-evolving probability density yields a picture of the decay mechanism, and points to the origins of structure in the product distributions.