According to reports, Mr. Choi was found with a note in his pocket that read, "I will be shooting tomorrow. I want to kill everyone and commit suicide. I don't know when it started, but I don't know why I live anymore." He continued, "I want to kill everyone and I wish I died too," and, "I regret not killing everyone and committing suicide during GOP (isolated general outpost)." 

Everything else on the note alluded to committing suicide and killing others. 

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During a gunnery exercise with 200 other reserve soldiers, it was reported that Mr. Choi fired his first round at the target before firing six other rounds at the soldiers around him. Four reserve soldiers were shot before Mr. Choi fired the eighth round at his head. 

The four wounded were rushed to different hospitals for immediate care. However, one reserve soldier, identified as Mr. Park, passed away from his gunshot wound. 

The reason for Mr. Choi's actions are still being investigated as one military official stated, "We are investigating the exact details of the incident through fellow reserve soldiers and other executive management officials. The reason for the attack is taking a while to uncover because the attacker took his own life."