Update 2: Mercury News has a bit more information about where the news of Jackson's death came from.
Update 3: More information from LA Times. Jackson was in a deep coma and died not too long afterwards.
This is perhaps one of the most shocking deaths in a while. He was only 50 years old and one of my favorite musicians. Say what you will about his personal life, his weirdness, his plastic surgery, etc., the guy knew how to be an entertainer. You don't even have to have liked his music or his style to understand what he did almost single-handedly to music. And there has never been someone with as much charisma and power on stage as Michael Jackson--though one could certainly argue that Elvis and Jackson were on equal planes.
In any case, it is unfortunate that Mr. Jackson has left us. He had, apparently, made plans for, a comeback tour in London and now we will never see him in action again. He will be sorely missed, but remembered for the power of his music and his performances.
To say a proper goodbye, I would love to embed a video of my favorite Michael Jackson song, but unfortunately the feature has been disabled on YouTube. So, I'll just link you to the music video for Thriller, one of his most iconic works of musical art.
Goodbye Michael, and may you find piece wherever you are now.