MADRID (MarketWatch) — Shares of GoPro Inc. GPRO, +4.82% sank 11% in premarket trading on Friday. The maker of wearable video cameras posted results that easily beat expectations late Thursday, but then warned on the upcoming quarter. GoPro said during its earnings call that it sees first-quarter earnings between 15 and 17 cents per share, against Wall Street expectations for earnings of 17 cents, according to Reuters and CNBC. As well, GoPro said Chief Operating Officer Nina Richardson has resigned effective Feb. 27. Shares swung wildly overnight, climbing on news of the results, only to subsequently fall sharply.