Brown, 18, was shot to death by officer Darren Wilson on Aug. 9 after the officer allegedly stopped the teen for walking in the street with a friend.
Some witnesses said Brown had his hands up during the incident and didn't provoke the shooting, while others said Brown attacked Wilson.
As protests ease in the eastern Missouri city, the U.S. Justice Department is preparing to investigate the police department's practices and training, officials told CNN.
A state official said Justice Department representatives met with Ferguson officials Wednesday to inform them of the planned investigation.
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