Thanks a lot, Cain!

[Belix]

What happened here?

In Diablo 1 (but not 2), you can wear items that are unidentified. Most magical properties on such an item will not affect your character while equipped, however, once identified their effects are applied immediately.

Unfortunately for this player, he had picked up and equipped some armor with -6 to Life, and had 6 or less hit points left when Cain identified it.