There are so many factors that go into the death of an animal. More than likely the animal had either some illness like an RI or coming from Petsmart it could have even had worms, or some kind of congenital defect that gave out.. I've had it happen where animals are perfect for years with me and then just one day you walk in and poof its dead.. In fact it happened to a 2002 hypo I had. It was a breeder and one of the original hypos around and I had it for 6 years and then just one day poof it died..

In short there's no telling really.