According to the Seeking Alpha portal with reference to traders, the investment bank acquired 3.7 million Activision Blizzard shares at a price of $72.25 apiece.
Journalists pointed out that Goldman Sachs paid $23.68 less per share than Microsoft offered as part of the takeover deal for the publisher. This may mean that the market is not fully confident that antitrust regulators will approve the transaction between the companies.
Note that Goldman Sachs acts as a financial advisor to Microsoft in a deal with Activision Blizzard.
UPDATE: Goldman Sachs sold, not bought shares.