You see, I came across a most curious object. In the midst of disenchanting it so that it could be used for its original purpose, I was Cursed. The Curse began in my hand and traveled up my arm. I expect I only had a year to live. However, before that year was up, I was finished off, shall we say, by the Killing Curse.

[Of course he had wanted to be killed by Severus, but that just complicates matters.]