A lot of companies come out with negative news on Friday afternoons in order to lessen the impact of such news. My guess is that negative news has leaked. Why else would this stock be down so much on no news as of yet? IMHO.
A buyout is a positive thing. I don't expect people would be dumping unless they were terribly ignorant or knew something negative might be in the wind. The individual investor is the last to know, and usually ends up holding the bag. IMHO.