I started working in HR-ish functions shortly after college. It took a few years before I got to make hiring decisions, but it happened eventually. The first position I was to fill was an Admin for a client's leadership (middle manager over ~300 people). After interviews we ended up with a super bright and professional lady. Her fake name for this story will be Sarah. Sarah always had the biggest smile, was super positive, and everyone loved having her on the team.
Three months later, the client calls me. "painturd, we need to talk about Sarah." "Is everything ok?" "No, it really isn't. Do you have her emergency contact information? You need to get in touch with her mom. She needs to come to the hospital. We are heading there now too." Several hours of juggling calls to family, the General Manager, our parent corporation's Legal and HR teams, and a federal investigative body ensued. Sarah had jumped off a seven-story parking garage, which was on site at the federal facility we were supporting.
TL;DR: My first hire killed herself at work, triggering a federal investigation.