Vandals have attacked stores in Ferguson, hours after police said the unarmed black teenager whose killing by a white officer unleashed days of rioting was a robbery suspect.
The allegation reignited anger in the town, a St Louis suburb in the state of Missouri, with the 18-year-old student's family accusing police of attempting to demean his character as the investigation into his shooting continues.
Ferguson Police linked Michael Brown to the theft of a $US49 ($A53) box of cigars from a convenience store shortly before he was fatally shot by police on August 9.
Police released surveillance footage showing a tall, muscular black man - in a T-shirt, khaki shorts and sandals, the same outfit Brown was wearing - grabbing a store clerk by the shirt and shoving him.
Following a large and peaceful demonstration Friday in the Missouri town that ended around midnight, groups of rioters struck several stores, including a mobile phone store and a meat market, the St Louis Post-Dispatch and other local media reported.
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Police in some areas fired tear gas and smoke bombs, but mostly stayed at a distance in armoured vehicles and riot gear, according to news reports.
In several instances, locals rushed to the stores being raided and convinced the looters to stop stealing and leave, then stayed to prevent the thieves from returning.
"If you're getting conflicting reports, it's because there's chaos here. It's dead in some areas, crazy in others.#Ferguson," wrote BuzzFeed reporter Joel Anderson on Twitter.
A barrier of locals stood outside the store that Brown allegedly stole from and stopped looters from breaking in, CNN reported.
The link between Brown and the "strong-arm" theft of a box of Swisher Sweet cigars, about 20 minutes prior to the shooting, appears in a police incident report that summarised the content of a surveillance video.
"The video reveals Brown enter (sic) the store" with his a friend and engaging in "an apparent struggle confrontation" with a store clerk.
"It is worth mentioning that this incident is related to another incident (in which) Brown was fatally wounded involving an officer of this department," the report added.
Through their lawyers, Brown's family said they were "beyond outraged" at what they called a "devious" attempt to smear the character of their son, who had no criminal record and was about to start vocational college.
"There is nothing based on the facts that have been placed before us that can justify the execution-style murder of their child by this police officer as he held his hands up, which is the universal sign of surrender," the lawyers added.
Ferguson police chief Thomas Jackson identified the officer who shot Brown as Darren Wilson, 28, a white, four-year veteran of the force with no record of ill-discipline.
"Initial contact between the officer and Mr Brown was not related to the robbery," Jackson said later.
Rather, he said, Wilson - in a patrol car - had stopped Brown "because he was walking down the street, stopping traffic. That was it."
