BlackBerry Ltd. bidder Fairfax Financial Holdings Ltd. walked away from a $4.7 billion takeover plan, sending the stock plunging as the company attempts to recover with a management shakeup and $1 billion bond deal.

Rather than acquiring the company, Fairfax will invest $250 million in the convertible bonds, according to a statement Monday. As part of the new agreement, Chief Executive Officer Thorsten Heins will step down from the company. Former Sybase AG CEO John Chen will become executive chairman, putting him in charge of the company's strategy.

BlackBerry shares fell as low as $6.27 in premarket trading after closing at $7.77 on Friday. The stock was already down 35 percent this year before Monday tumble.