Lisa Gassner, an assistant chief of the DeKalb County Police Department, will take over as interim chief later this month.

Gassner, the department’s first female major, will serve until the county can name a permanent successor to Chief William O’Brien, who is out of the office and using leave time until he retires on Nov. 30.

Gassner is a 28-year veteran of the department, serving in the robbery/homicide unit, narcotics unit and Strike Force. She also was a sniper on the force’s SWAT team.

She has not applied for the permanent job. However, two other assistant chiefs have: D.A. Holmes of the uniform division and A. Williams, head of special operations.