What is the connection? the same date? that's it? That's pretty weak.
Two identical dates, plus similarity of method and purpose. How much more evidence could there be at this stage? It merits further investigation.
By the way, the CDC now thinks there is an undiscovered letter, mailed before Oct. 24. This could be the hypothesized Oct. 12 letter in the article. http://www.freerepublic.com/focus/fr/570240/posts