Tesla CEO Elon Musk acquired a 9 percent stake in Twitter.

Elon Musk becomes the biggest stakeholder of Twitter.

The ultimate aim of Musk’s 73.5 million share purchase, worth about $3 billion, is not known.

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.

A U.S. Securities and Exchange Commission filing made public on Monday says the event triggering the filing happened March 14.

Yet Musk has also raised the possibility, publicly before his massive and loyal Twitter following, that he could create a rival social media network.

CFRA Analyst Angelo Zino wrote that although Musk’s intent is unclear, Twitter could be viewed as an acquisition target because the value of its shares have been falling since early last year.

“Musk’s actual investment is a very small percentage of his wealth, and an all-out buyout should not be ruled out,” wrote Zino, who covers Twitter and social media.