The hedge fund manager said his fund began buying Uber shares in early January and has amassed 30.3 million shares, worth $2.3 billion.

Bill Ackman said his hedge fund Pershing Square Capital Management owns 30.3 million shares of Uber Technologies Inc., citing the strength of the rideshare company’s management and saying that its stock is undervalued.

Billionaire hedge fund manager Bill Ackman revealed on Friday that his activist investment firm has bought up approximately $2 billion worth of shares of Uber — sending the ride-share company’s stock surging.