A demonstrator hurls a tear gas canister back towards police lines in Fergusson, Missouri, after an apparent peaceful demonstration was broken up by heavily armed police officers overnight.
Police chief Thomas Jackson, who has been the public face of the city torn by the death on Saturday of Michael Brown, 18, said earlier that the St Louis County investigation of the shooting could take weeks to complete.
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The Hollywood actor died of complications from surgery, according to reports.
Celebrities lined up to be photographed with the characters, who famously have antennas on their heads and TV screens on their stomachs.
The Olympic champion released a statement after a newspaper alleged his American coach may have broken anti-doping rules.