Brown was fatally shot by Wilson last August, sparking numerous protests in Ferguson.
"We believe that there were other alternatives available to him," Daryl Parks, attorney of Michael Brown's family, said of Wilson. "He did not have to kill Michael Brown."
Attorney Anthony Gray, speaking on behalf of Brown's family, said they "disagree with those findings."
Michael Brown's parents, Lesley McSpadden and Michael Brown Sr. attended the news conference but did not speak to reporters.
Also this week, the Department of Justice also released a scathing report that found the Ferguson Police Department had a pattern and practice of discriminatory policing.