The announcement that Lululemon's CEO, Christine Day, will step down was a bad decision, CNBC's Jim Cramer said, and investors should sell the stock, even after a drop in share price following the news.

"I thought this was staggering," Cramer said. "The timing could not have been worse to bring in a new person to lead … She's gone and I don't know who is going to run Lululemon"