A high school friend of mine killed herself a couple years back when we were living up in Seattle.
Two days before the fatal event, she came to a party I hosted. At 3AM, when everything was wrapping up, I exited my hallway bathroom, ready for bed... she confronted me outside the door, and said, "I just wanted to let you know that I wrote a book and you are in it", she was smiling.
I told her I was flattered, and asked for more information, she said it was a story about her life, and I had been her first 'crush' in 3rd grade. I thanked her for telling me that, and we hugged and said goodnight. The next day, we all had breakfast together... everything was normal.
One day later, I realized that she was saying goodbye to me that night. It was completely premeditated and she gave no outward signs to anyone that there was anything wrong. Unlike many women, she chose to use a gun, which indicated that this wasn't a 'cry for help', she wanted a final release from her suffering.
After the event, I learned that she was in treatment at the time for severe depression - I never knew. Her family never told anyone (can't see why they would) and she never told me. I privately asked myself why someone who was depressed would move to SEATTLE of all places, but that's besides the point.
I just wanted to post this and remind everyone how insidious mental health issues can be. What may appear calm on the surface may actually be a whirling vortex underneath.
Take the time to really get to know your friends and find out how they are doing. Their lives may depend on it.