How to react

Today, my friend told med that her sister had threadended to kill herself. She had dissappeared and her, her mother, her sisters friends and parents had to go looking for her. Luckily they found her alive, but now her sister won't stop crying and she won't tell why.
When my friend told me this I was shocked. But the worst thing was that I had no idea how to react on it. Of course I comforted her, I let her talk instead of me giving a lecture or something. I doubt that would have been helpfull. But this reminds me of another time not that long ago, a couple of weeks maybe where my other friend told me that her friend had tried to kill himself as well, and ended up at the hospital. Again, I was shocked and had no idea what to say. So what to do when someone tells you a story like that? What do they want? What would be the best to say? It's kind of hard isn't it.

- xo Elk