Stocks sink after weak profit report from Walmart

Wall Street opened lower Tuesday, dragged down by weak profit reports from some of the biggest names in corporate America. 

The S&P 500 fell 29 points, or 0.7%, to 3,927 points shortly after the start of trade, while the Dow Jones Industrial Average slid 0.5%. The tech heavy Nasdaq Composite dropped nearly 1%.

Walmart shares are plunging after the nation's biggest retailer lowered its profit forecast and said surging inflation on basics like food that is making shoppers cut back. GM is down 4% after saying computer chip and parts shortages hobbled factory output in the second quarter.