The 9 October letters were mailed after Bob Stevens' death. They knew they were playing with fire.
I agree. Furthermore, this claim that the perp/s really only wanted to scare people and not actually kill anyone has always struck me as being completely absurd. The anthrax in those letters was the deadliest stuff the top experts had ever seen before. Whoever prepared this stuff absolutely HAD to know that it would almost certainly kill anyone who got into close enough proximity of it.
There is no doubt that they knew that they had killed Bob Stevens before mailing the 9 October letters. A reference to Stevens' death dated 5 October: http://groups.google.com/groups?selm=3BBE2232.89CC8E1F%40sympatico.ca&output=gplain. This is a reply to an earlier article which, curiosely, was posted anonymously - by "R." - and marked with the x-no-archive tag to request that it be not saved by search engines. Why the superanonymity? Who was this "R."? May-be one of the mailers, just possibly? Doesn't really matter.
The earliest the letters postmarked 9 October could have been mailed was late in the day on 6 October. By the time of mailing, the mailers had known for at least a day that Stevens had died.
I agree with Battle Axe that the envelopes were probably addressed before being filled. Common-sense says that people don't take chances with anthrax-filled envelopes. There is no way to tell how long before mailing were they filled. It doesn't matter for the conclusion tho - they proceeded with the Daschle-Leahy mailing even after they knew that Stevens had died.