I agree with most of the theories so far -- workplace rage. But, I also agree that it just seems like there must be more to this. An affair is one possibility, but if that was the case, there might well be rumors in the lab -- hard to keep 100% secret. I keep going back to some sinister issue with research and financial stakes, or the pride of researchers. Here is an article that shows the stakes people will go to in regard to the fruits of research. I just wonder if Annie had made a major discovery that others wanted credit for, or maybe she discovered that someone else's research was wrong and it was going to hurt someone's royalties.
In the above case, notebooks were allegedly tampered with and falsified which which led to an arrest, and a Judge's life was threatened. Maybe Annie had some evidence, and Clark was paid to get that evidence or threaten Annie to back off.
[Relevant IPBiz post: http://ipbiz.blogspot.com/2004/07/criminal-actions-in-patent-litigation.html]
The Yale case even created comment at Boise State:
"Well Boise State is a safe place to live and learn," said Frank Zang, BSU spokesman. "But anytime that you have a violent crime, such as what we've seen at Yale University or in the past at (Virginia Tech), it certainly does heighten awareness for personal safety." [http://www.2news.tv/news/local/59677157.html ]
One can also think back to Ted Streleski at Stanford.