Ferguson Mayor James Knowles says one police department employee was fired over racist emails uncovered in a Justice Department investigation into the city's law enforcement practices.

Knowles' comments at a press conference Wednesday were the first response from city leaders to the federal investigation that found systemic racial bias in law enforcement in the St. Louis suburb of Ferguson.  

Two additional officers resigned following the probe's discoveries, according to the St. Louis Post-Dispatch, which reported Capt. Rick Henke and Sgt. William Mudd resigned Thursday.

The Justice Department report said police work was focused on generating revenue from black residents from fines and fees, rather than protecting the community.

In a separate report released at the same time, the Justice Department cleared Darren Wilson, the white former officer who fatally shot Mike Brown in August.

The Associated Press contributed to this report.