The person who sold around $200 million of GME shares on May 2 is James Kim, the founder of EB Games. When GameStop bought EB Games he received $440 million in cash and about 18.25 million shares of GameStop. He has since cashed in about $660 million worth of the GameStop shares he received.
To date Kim has cashed in around $1.1 billion from the GameStop take over of EB Games and now has less than $100 million worth of Gamestop shares remaining.
As you point out Leonard Riggio has also been selling shares. He's the guy who founded Barnes & Noble and bought and put together several video game chains to form GameStop. He has sold more than $150 million worth of GameStop shares in the last year.
These guys selling is raising all kinds of red flags for me too. I love GameStop: the shares of the company have risen much more than I imaged possible when I bought first bought shares of GameStop 2 years ago. I've taken out profits that more than cover the cost of my shares but with after the news of these these guys selling I placed a limit order to sell my shares.