People of Reddit, have you ever saved someone's life? If so what were the circumstances?

After that AskReddit about killing people, I think we need uplifting, inspirational stories of lives that Redditors have saved.

I once stopped my sister from falling into the Grand Canyon. My family was visiting the Grand Canyon for a few days, and myself, my dad, and my sister were out at dusk walking to dinner. My sister was walking along a chain-link fence that ran along the edge of a pretty steep drop-off. She had her eyes clothes, and was leaning her weight onto the fence as she walked, so that she kind of glided along on the chain. She was about three feet from the end of the fence, which was not the end of the drop-off, when I shouted at her to stop. She opened her eyes and stopped just in time to prevent herself from walking right off the edge. If I hadn't said anything, I truly believe she would have pitched right over.

Redditors, tell us about those times where you saved a life?