While driving the vehicle at highway speed, the vehicle did not respond as expected during braking. Upon attempting to slow the vehicle, control was lost, the vehicle became unstable, left the roadway, and rolled. As a result of the incident, the driver sustained serious injuries requiring emergency transport and hospitalization. No warning lamps, messages, or brake-related alerts were observed prior to the incident. After the crash, the BMW mobile application displayed a brake system malfunction warning indicating an integrated system brake failure, with a timestamp shortly after the incident. The vehicle has not yet been inspected or diagnosed by a BMW dealer or independent service center. The vehicle remains available for inspection following the crash and has been retained post-incident pending salvage processing.