Brooklyn District Attorney Ken Thompson was officially sworn in Sunday at Steiner Studios at the Brooklyn Navy Yard.
Thompson is the borough's first African-American district attorney.
In his speech, Thompson addressed gun violence in Brooklyn and the ways his office will work to stop it.
"We will create a new crime strategies unit in the Brooklyn DA's office that will work proactively with the police to identify and focus on those individuals who carry illegal firearms and engage in violence in our neighborhoods," Thompson said.
Thompson succeeds Charles Hynes as Brooklyn DA.
Hynes served in the position for 24 years before being beaten by Thompson last year in both the Democratic primary and the general election.