It seems clear that people were trading on information relating to the delisting before the 4:30 information release. This is serious stuff and easy to track by the SEC, so it's just plain stupid. I've seen this before at a company I used to work at. First the SEC sets up meetings with everybody at the company that was privy to the information. Then they give you a list of names of people who traded the stock, and ask if you know any of them. The point is to get you on record, possibly telling a lie. Then they dig phone records, personal financial accounts, conduct interviews etc. to get to the truth. If they catch you lying, you get the maximum jail sentence for a stupid decision made by you or your friends/family that got only a little pocket change.