Tesla CEO Elon Musk has taken a 9% stake in Twitter
He become its largest shareholder after raising questions about the social media platform's dedication to free speech.
The ultimate aim of Musk's 73.5 million share purchase, worth about $3 billion, is not known.
Yet in late March Musk, who has 80 million Twitter followers and is very active on the site, questioned free speech on Twitter and whether the platform is undermining democracy.
It's unclear just when Musk bought the stake.
His stake meets the criteria for being a long-term “passive” investor, one looking to minimize buying and selling of the shares.
Yet Musk has also raised the possibility, publicly before his massive and loyal Twitter following, that he could create a rival social media network.
Musk told his more than 80 million followers on Twitter that he was " giving serious thought " to creating his own social media platform and has clashed repeatedly with financial regulators about his use of Twitter.
His Twitter stock purchase comes as Musk is locked into a bitter dispute with U.S. securities regulators over his ability to post on Twitter.
Musk has not spoken specifically about how he would change rules at Twitter, but the social media platform's history of suspensions and bans is well documented.