Hahn was sworn in during a ceremony at his alma mater, Sacramento State University, followed by a community party at McClatchy Park in the Oak Park neighborhood where Hahn grew up.
He most recently served six years as Roseville's police chief. Prior to that he spent over twenty years with the Sacramento Police Department.
In an interview with FOX40 Hahn said his first two priorities will be building the community's trust in the police and raising morale within the Sacramento Police Department.
“Law enforcement needs to evolve," Hahn told FOX40. "Our country has evolved, the circumstances have evolved and we need to evolve with that, and part of that is transparency. We're public officials, we wear a uniform, name tags and badge numbers, and so, the community has a right to know what their police department does and I think the transparency piece goes right along with that."
Mayor Darrell Steinberg attended the ceremony and welcomed Hahn in a tweet.