After 35 years at the company — the last six of them as CEO — Target’s top exec Gregg Steinhafel has stepped down less than half a year after the retailer was the site of a massive data breach that compromised credit card and personal information for more than 100 million customers at the height of the holiday shopping season.

“It has been an honor and a privilege to lead this great brand and work alongside what I believe is the best brand in retail,” wrote Steinhafel, who was also the company’s President and Chairman, in his statement explaining his decision to step down effective immediately.

Last fall, hackers were able to access Target’s in-store card payment processing system via the network of a third-party HVAC contractor. Beginning around the busy Black Friday shopping weekend, and continuing through mid-December, cards swiped at Target stores around the country were unwittingly collecting and transmitting customers’ information to the cybercriminals.

Relative to the size of the breach, the damages to customers was minimal, as many affected consumers canceled cards that may have been compromised. However, these millions of new cards and accounts came at a huge price to the banks and credit unions, some of which have filed suit against Target to recoup expenses.

“The last several months have tested Target in unprecedented ways,” continues Steinhafel. “From the beginning, I have been committed to ensuring Target emerges from the data breach a better company, more focused than ever on delivering for our guests. We have already begun taking a number of steps to further enhance data security, putting the right people, processes and systems in place. With several key milestones behind us, now is the right time for new leadership at Target.”

In addition to the data breach disaster, Steinhafel was CEO during the early months of Target.com’s relaunch in 2011. With frequent crashes, poor customer service, mysterious inventories, and missed delivery dates, Target’s first truly independent foray into e-commerce was a major mess, resulting in the early exit of Target.com President Steve Eastman only a few months after the site’s relaunch.

Target’s Chief Financial Officer John Mulligan is taking over the reins from Steinhafel at President and CEO, at least temporarily, while the board searches for a new top executive. Boardmember Roxanne S. Austin has been named as interim nonexecutive chair of the board.

“The board is deeply grateful to Gregg for his significant contributions and outstanding service throughout his notable 35-year career with the company,” reads a statement from the retailer’s board.