Responses
I bet he k*lled himself after finding out that he murdered FL/coming back to his sense. And i think in the end FL did marry the crown prince and tried to push him away thinking he would be hurt if he has feeling for her but instead it made him crazy and obsessed
Based on chapter 25 , i think Haewon has some Double Personality and the other personality is the assassin one and that personality misunderstood FL by a lot especially since her father was an ass to that side of personality. He might questioned that FL all kindness and sincerity was just fake and all an act. And i bet even in the past life, when Killian came to his sense he was found crying