He mentions her by name in the first paragraph (after the cover letter):

> I don’t post directly because I am in prison for killing my wife Nina in 2006.

He doesn't get into whether/why he is sorry:

> I am very sorry for my crime–a proper apology would be off topic for this forum, but available to any who ask.

Hans Reiser has previously explained why he believed the murder was justified. It is not clear to me, from this letter, whether he still believes so.