Transcripts show Choi Sang-yeol made three announcements advising passengers in train 1080 to remain seated while he attempted to reach superiors. Finally, he was advised "Quickly, run somewhere else. Go up... kill the engine and go." Choi then opened the doors and fled, but in doing so he removed the master key, which led to a shutdown of the onboard batteries that powered the train doors and effectively sealed passengers inside. Later investigation showed that 79 passengers remained trapped inside train 1080 and died there.