Tesla CEO Elon Musk has grabbed a huge stake in Twitter, making him the social media giant’s biggest shareholder just days after questioning its commitment to free speech.

Musk’s purchase, revealed in a Securities and Exchange Commission filing published on Monday, gives him a 9.2% ownership stake, according to the Financial Times. At Twitter’s current valuation, Musk’s purchase likely cost nearly $3 billion. It comes after a poll Musk posted on Twitter sparked speculation that he was considering buying Twitter or launching his own social network.