CNN has obtained new cellphone video in which two white construction workers witnessed the shooting of the 18-year-old African American man and reproached police officer Darren Wilson for having shot someone who "was no threat at all".
"The cop didn't say get on the ground. He just kept shooting," one of the contractors, who appears on the video, told CNN.
The witness, who did not want to have his identity revealed, describes how the officer shot Brown in the head when he had his hands raised.
Witnesses says Brown was no threat at all to the police officers
A second man appearing in the video confirmed that Brown had his hands up and began to try and flee from the officer, who pursued him and shot him to death.
These details will be crucial in determining whether or not police abuse was committed in the Aug 9 shooting and they have once again sparked suspicion and complaints of racism in mainly black Ferguson's overwhelmingly white police department.
The US Justice Department has opened an investigation to clarify the circumstances surrounding Brown's death and to better understand the operating practices of the Ferguson police.
The death of Brown, who was unarmed, at the hands of a white police officer and differing versions of the incident on the part of police and witnesses resulted in weeks of street disturbances in Ferguson.
Several people were arrested on Wednesday for trying to block Interstate 70 in Ferguson to protest the shooting.