GameStop today announced the resignation of chief executive officer Michael K. Mauler, who left the company “for personal reasons, effective immediately.” Mauler was CEO of GameStop for a surprisingly brief stint; he was appointed to the position in February 2018. Daniel A. DeMatteo, executive chairman of the board of directors for GameStop, will serve as interim CEO. DeMatteo is one of GameStop’s co-founders and served as interim CEO after J. Paul Raines left the position for health reasons in 2017. Raines died in March, one month after Mauler was named as his successor. GameStop did not disclose or expand upon the reasons for Mauler’s resignation. Mauler was a 16-year veteran of GameStop, and his resignation is “a shocker and disruptive,” Wedbush Securities analyst Michael Pachter said in a statement to the Wall Street Journal. In March, GameStop reported positive growth in sales for games and collectibles at its stores, partly driven by strong Nintendo Switch sales, but offered poor guidance for the coming year. The company expects sales to be flat or down in 2018.