Complex sentence: At graduation, he plants a bomb in the lecture hall and plans to activate it after his speech, but the bomb goes missing; he then receives a call from Moriguchi telling him she moved the bomb to his mother's office, killing her.
Split into simpler sentences: At graduation, he plants a bomb in the lecture hall and plans to activate it after his speech. But the bomb goes missing and he receives a call from Moriguchi telling him she moved the bomb to his mother's office, killing her.