DeKalb County Sheriff Thomas Brown on Wednesday will formally announce a campaign for Congress in a Democratic primary challenge to U.S. Rep. Hank Johnson.

Brown has scheduled announcement events in Decatur, Lilburn, Conyers and Covington. He has been hinting at a run in the 4th Congressional District for months and formed an exploratory committee. He has been among the county’s top public safety officials for decades, serving as fire chief and public safety director before becoming sheriff in 2001.

Johnson, of DeKalb County, won the seat after defeating then-Rep. Cynthia McKinney in a 2006 Democratic primary runoff. The seat is weighted heavily toward Democrats.