What: Shares of Shutterstock (NYSE:SSTK) were down about 31% just before 1 p.m. EDT Thursday after reporting its second-quarter financial results earlier in the morning and the unexpected announcement that its CFO would leave the company.

So what: Shutterstock posted mixed results in the eyes of investors, with revenue growth of 30% just slightly missing expectations but earnings of $0.31 per share topping the consensus forecast by a penny. Yet the company's third-quarter guidance was much weaker than expected, with Shutterstock projecting revenue for the current quarter of $105 million to $108 million and adjusted operating earnings of $18 million to $20 million. Both figures imply much slower growth rates than investors had hoped to see.

Even worse, Shutterstock cut its guidance for the full 2015 year. The image specialist reduced its expected revenue from an initial range of $436 million to $444 million to a new projection for between $425 million and $430 million. A similar cut of around $8 million to $9 million in adjusted operating earnings to a new range of $82 million to $85 million pointed toward slowing growth for the company.

Finally, news that CFO Tim Bixby would leave Shutterstock by the end of September further concerned shareholders. The company said that former board member Steven Berns would become the new CFO, with the succession occurring on what seems to be amicable terms.

Now what: The big concern for Shutterstock shareholders is that with the stock trading at extremely high earnings multiples, even the hint of slowing growth is enough to send investors into a panic. Moreover, although Bixby's resignation seems unconnected to the company's financial performance, having the announcement come at a time of slowing forward guidance is always going to cause short-term nervousness. Shutterstock saw considerable strength in its internal metrics, and it needs to keep boosting revenue and download traffic in order to stay on its thus-far impressive growth track.