U.S stock markets struck a two-week low today as several new items fueled growing investor bearishness. After Dow component Caterpillar (NYSE: CAT) cut its 2015 profit forecast amid a growing slowdown that has driven mining and construction dealers to trim their orders from the industrial power, shares of the company sold down 4.3%. That drop helped drag the Dow Jones Industrial Average (INDEX: ^DJI) 0.8% lower as well.

That wasn't the only negative news to affect market sentiment. Equally alarming to investors, the head of the Philadelphia Federal Reserve, Charles Plosser, stated publicly that the U.S. Fed's most recent stimulus efforts were unlikely to bolster economic growth.

Today's market news caused the S&P 500 and the Nasdaq to end 1% and 1.4% lower, respectively. As should be expected, the glut of negative commentary also generated a sharp spike in the market's "fear gauge," or the VIX (INDEX: ^VXX), which gained 7.9% on the day.

Around the markets
Shares of Zillow (Nasdaq: Z) at one point today tanked slightly more than 3%. The driver? Short-selling research firm Citron Research issued a report that proved highly critical of the online real estate service. According to an AP report, the "story Zillow has been telling Wall Street is completely inconsistent with [the] company's underlying business metrics." The company has, though, grown its revenue at a greater than 100% greater clip in five of the past six quarters. Although in the one quarter where it failed to match the triple-digit growth -- last quarter -- it still grew sales at just over 75%.

On the flip side, Research In Motion (Nasdaq: RIMM) rose significantly today as the beaten and bruised cell-phone maker previewed its most recent update to its lagging smartphone line. The company hopes its next-gen line of phones, powered by an operating system that's already several times delayed, will help it win back favor from consumers who have continually defected to other mobile operating systems over the past several years. Although the BlackBerry maker is cheap, I wouldn't bet on a comeback.