Tower-shaped rock masses are particularly susceptible to failure, via fracture and disintegration, due to their inherently large height-to-diameter ratio. A rockfall event at the Zengziyan Cliff, in Chongqing, China, was selected for a case study. Based on video footage, the movement characteristics of the initial failure processes were analyzed in three movement stages: initiation, acceleration and deceleration. The failure process began at the bottom of the tower-shaped unstable rock mass and manifested itself in the form of fissure extension followed eventually by disintegration. The acceleration curve presented a continuous negative fluctuation associated with buffering in the deceleration stage. At the same time, the movement characteristic curves at different measurement points displayed significant time-dependent differences, proving that cracking, collisions and disintegration occur in the failed rock mass during the initial failure process. The results of this analysis provide a reference for the early identification of similar rockfalls and for analysis of their mechanisms.