The contact owns a 2016 GMC Yukon. The contact stated that while driving at approximately 70 mph, the brake pedal was hard to depress and the brake pedal traveled to the floorboard. The contact mentioned that the brake pedal needed to be pumped in order for the vehicle to be operated. In addition, the contact stated the vehicle failed to stop immediately. The vehicle was taken to a dealer where it was diagnosed that the brake line needed to be flushed. The vehicle was repaired however, the failure persisted. The vehicle was taken to an independent mechanic where the failure was undetermined. The contact mentioned while the mechanic was reversing the vehicle the brakes failed to operate causing the vehicle to crash into a person and a vehicle. The contact stated that the lady sustained multiple injuries that needed medical attention. A police report was filed. The vehicle was towed to the dealer where it was diagnosed that the brake vacuum pump needed to be replaced. The vehicle was repaired but the failure recurred. The vehicle was taken back to the same dealer where they informed the contact that the failure was unable to be duplicated. The vehicle was not repaired. The manufacturer was notified of the failure. The approximate failure mileage 54,000.