I would actually say something more like this:
"As an observer, I have seen how life can change in one minute."
I think that "can change" sounds more natural. Also, I might use the word "instant" instead of "minute". So really I would say, "As an observer, I have seen how life can change in an instant." I think this way sounds best, but I don't know if you want to change your original sentence that much. Hope this helps :)