FERGUSON, Mo. — The unrest in Ferguson began one week ago, on the quiet side street of Canfield Drive, when residents were startled by a series of gunshots and poured out of their homes. They watched and wept as the police stood guard for hours over the body of 18-year-old Michael Brown, splayed face down in the street.

But over time, the demonstrations have changed to become an amalgam of peaceful protesters — some furious about what they say is endemic abuse of African-Americans by the police — and separate groups that have carried out acts of violence and looting.

Early Saturday morning, the divisions became even more evident during a four-hour standoff with the police. One group, some of its members wearing bandannas, broke into a liquor store and left clutching bottles of alcohol. But at other retail outlets, like a beauty supply store, demonstrators blocked the looters’ way.

Arguments ensued on the streets, with some people pleading to avoid confrontations, while others tried to encourage the crowd to take on law enforcement officers.