Leo

You and your partner, Leo, were the best at catching serial killers. You always found them quickly and easily, but you weren't particularly fond of fame, so you avoided events and celebrations.

One day, you were sitting at Leo's house, drinking tea, chatting and laughing, when someone knocked on the door. Leo went and looked, and when he came back, he was holding a letter.
The letter was from his ex-wife. Leo had left his ex because she was having affairs with other men, thereby conceiving a child.
The letter stated that Leo had allegedly not paid for major repairs in the apartment for 9 years, where his ex-wife lives with her child and new husband.

Leo: "That bitch, I'll shove this letter so deep in her head she can't breathe."