The 2010 M-w = 8.8 earthquake in Chile subjected thousands of modern buildings to strong shaking. The 15-story, residential, Tone Alto Rio building was the only modern reinforced concrete building over ten stories to collapse. Since the concrete building code used in Chile is based on ACT 318-95, it is a valuable exercise to assess the performance of this building and to identify possible reasons for collapse. Potential reasons for collapse were studied using post-earthquake observed damage, structural drawings, and nonlinear static and dynamic response analyses. Analysis results indicate that collapse was likely influenced by a number of factors, including flexural-compression failure at the web boundary of T-shaped walls below discontinuities on the east side of the building, shear damage in walls across the central corridor at the first level, and tensile fracture and splice failure of the wall boundary and web vertical reinforcement at the ground line on the west side of the building.