Elon Musk caused a bang: The CEO of the electric car manufacturer Tesla and the aerospace specialist SpaceX is now also a major shareholder of Twitter.
According to a statement to the US Securities and Exchange Commission published on Monday, he has bought a 9.2 percent stake in the online platform.
The news caused tremendous movement on the stock market: Twitter's share price rose by more than 25 percent in pre-market trading.
Roland Lindner
Business correspondent in New York.
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The shares acquired by Musk are worth almost $2.9 billion based on the last price.
The Tesla boss can easily afford this, he is currently by far the richest person in the world.
The Bloomberg Billionaires Index puts his fortune at $273 billion.
Musk is an avid Twitter user himself and has around 80 million followers here.
He regularly attracts attention on the platform with provocative statements.
And he recently sharply criticized the company because, in his opinion, it hinders freedom of expression.
Almost two weeks ago, he conducted a survey on Twitter and asked whether the platform followed the principle of freedom of expression.
More than 70 percent of the users who voted said no.
Share purchase already on March 14th
Musk later tweeted that he was "seriously" considering starting his own online platform.
The fact that Twitter does not respect the principles of free speech undermines democracy.
But now he has joined Twitter himself.
As the SEC statement shows, he bought the shares on March 14, before the Twitter poll.
Now the question arises as to what he is planning as a major shareholder.
Analyst Dan Ives of Wedbush Securities told CNBC on Monday that he could imagine Musk trying to pressure Twitter for change.
A takeover is also conceivable.
In any case, Musk will not stop at just being a passive investor.
"That's just the beginning."