Extreme winds disaster occurred in Nanchang, Jiangxi Province in early morning on March 31, 2024, which is responsible for the fall of three residents from a high building. Based on SA dual-polarization Doppler weather radar observations from Nanchang and surface observations, this study analyzed the fine structure of the severe storm near the accident building. The results revealed that a bookend vortex was embedded in the northern end of the bow echo within a quasi-linear convective system around the time of the accident, with its horizontal scale and vertical vorticity comparable to that of a strong mesocyclone. Tornado vortex signatures (TVS) with tornado debris signatures (TDS) were identified in the center of the bookend vortex which passed over the accident building. The rotational velocity of the TVS exceeded 40 m·s-1. Damage surveys conducted along the tornado path identified by TVS and TDS revealed multiple tornadic damages, including strong cyclonic rotational winds, localized convergent rotational winds, debarked trees and complete collapse of stone bridges. This indicated that an EF2 tornado occurred very close to the accident building, most likely responsible for the fatal fall. It is noteworthy that the tornado-related vortices include a bookend vortex and several leading-edge misocyclones embedded within it, which emerged and intensified almost simultaneously in this event. The observational study on the formation mechanisms indicated that those tornado-related vortices resulted from the tilting of the horizontal vorticity. The horizontal vorticity is associated with the strong low-level vertical shear of the elevated rear-inflow jet and the baroclinic vorticity related to the gust front.