Why does a musician's death spike their album sales so much?

Like clockwork, album sales for Whitney Houston skyrocketed following her death, which is a trend I've never understood. I've always been fascinated by the sales figures aspect of the music industry and Billboard magazine, its bible, had some extremely interesting numbers published earlier today in relation to Houston. In the day-and-a-half following her death on Saturday afternoon (Billboard's weekly sales figures are tabulated through the end of Sundays), Houston sold an astounding 101,000 albums in the U.S., including 64,000 copies alone of her Whitney: The Greatest Hits album. Her previous week's total sales numbers? Just 2,000. And if you want another example of just how dead the CD format is, only 10,000 of that 101,000 sales figure was physical (CD or vinyl) album sales. On a related note, there's an amusing story here about Sony's embarrassing decision/mistake to jack up the price of a couple of Houston albums in the U.K. immediately following her death.

So exactly who is buying these albums in such quantities? The people most emotionally affected by a music figure's death (outside of that musician's friends and family, obviously) would be their loyal fan base, but wouldn't that group already own most of the artist's work? If not them, then I assume it's other people being caught up in the emotion of the moment, including: a) music consumers who were casual fans of the deceased musician, b) people who had always been on the fence about buying one of the musician's albums, or c) people who don't know anything about the musician and are so easily influenced by media saturation that they go and buy an album. Whoever's spending the money, I don't quite get it. It's almost like there's this weird urgency to pick up the dead musician's work now because people are afraid that they're not going to be able to hear anything else new from them and all the albums will disappear or something. But this is the music business after all...there'll be plenty of Houston outtakes, rarities, and repackaged greatest hits albums to come in the following years.