Carl Icahn has reportedly bought between 30 million and 40 million shares of Hertz Global Holdings, Inc. (NYSE:HTZ), according to CNBC‘s sources. Those sources also said that he was the target of the poison pill recently adopted by the car rental company. That poison pill, or shareholders’ rights plan, took effect on Monday. Hertz said it adopted the shareholder’s rights plan after noticing “unusual and substantial activity” in its stock recently.

Carl Icahn Hologic

Shares of Hertz rose initially after the news about Carl Icahn’s investment into the company. However, they fell back off throughout the day to remain less than 1% up from their opening price.

Carl Icahn nearly Hertz’s biggest shareholder

According to CNBC’s sources, Carl Icahn’s position in Hertz Global Holdings, Inc. (NYSE:HTZ) isn’t all in common shares. They said it includes some derivatives which reflect shares in the company. If all of those shares were common stock, then 30 million to 40 million shares would be almost enough to make the activist investor the biggest shareholder of Hertz.

Bloomberg data indicates that Wellington Management may currently be Hertz’s biggest shareholder. As of the quarter ending in September, the firm held 41 million shares, which made up a 9.2% stake in the company.

Loeb also bought Hertz shares

Icahn isn’t the only activist investor targeting Hertz Global Holdings, Inc. (NYSE:HTZ). Earlier this week, sources also told CNBC that Dan Loeb had also bought into the car rental company. In addition, Keith Mister, who’s with Corvex Capital and is a protégé of Carl Icahn, also increased his position in Hertz. He was said to have met with Mark P. Frissora, CEO of Hertz, over the last month. CNBC’s sources called that meeting a “constructive” one.

Carl Icahn himself has been pretty active of late, even targeting Apple Inc. (NASDAQ:AAPL) in his attempt to get the company to buy back more shares.