Wall Street slid paced by Boeing as investors worried about expenses for its 787 Dreamliner passenger jet, while oil fell after a report showed US inventories rose more than expected last week.
West Texas Intermediate crude for December delivery fell 1.5 percent. In afternoon trading in New York, the Dow Jones Industrial Average fell 0.57 percent, the Standard & Poor's 500 Index shed 0.35 percent, while the Nasdaq Composite Index declined 0.38 percent.
Part of the negative sentiment was linked to an attack by at least one armed man in Ottawa, Canada's capital. A soldier standing guard at the nation's war memorial was killed and the gunman, who ran into the main parliamentary building, was shot dead.
Slides in shares of Boeing and those of American Express, last down 3.8 percent and 1.6 percent respectively, propelled the Dow lower.
Shares of Boeing dropped amid mounting concern about costs for its 787 Dreamliner, overshadowing the company's upgrade in its earnings outlook as well as its better-than-anticipated third-quarter profit.