Bergen County, the state's most populous county and one of the most diverse, has a new top cop.

Mark Musella, previously a solo practitioner in Hasbrouck Heights, was sworn in as the new Bergen County prosecutor on Monday by Superior Court Assignment Judge Bonnie J. Mizdol at the Bergen County Courthouse in Hackensack.

Gov. Phil Murphy nominated Musella for the position on March 25, and he was confirmed by the New Jersey Senate on May 13.

Musella takes over from Dennis Calo, who has served as Bergen County's acting prosecutor since January 2018. Calo now becomes first assistant prosecutor under Musella.

“Mark Musella is an accomplished attorney with an exceptional legal career in Bergen County,” Murphy said in a statement. “I am confident that [he] will be a strong leader and enhance the trust between law enforcement and the community to promote a safer Bergen County for all.”

A lifelong Bergen County resident, Musella is returning to the office where he began his legal career as an assistant prosecutor, from September 1988 to June 1994. He eventually served as assistant chief of the Trial Section and the Grand Jury Section. During his tenure, he prosecuted 50 jury trials, and handled hundreds of pleas, sentences, bails and motions, as well as presented cases to the grand jury, the governor's office release noted.

“I look forward to serving all of Bergen County's diverse communities and to making our county a safe and better place to live,” Musella, a 1980 Bergen Catholic graduate, said in a statement.

Bergen County is home to nearly 1 million residents living in 70 municipalities, and is often one of the most sought-after counties to win in statewide and gubernatorial races because of its affluence and population.

Since 1994, Musella, who lives in Wood-Ridge with his family, has worked as an attorney in criminal and civil litigation and has served as municipal prosecutor in Hasbrouck Heights, as well as a public defender for 12 Bergen County towns, according to the release.

Musella is a 1984 Fordham University graduate and obtained his law degree from the Delaware Law School-Widener University in 1987. He began his legal career as a law clerk for the late Judge Ralph Polito, who served in Bergen County Superior Court for 15 years.

Attorney General Gurbir Grewal, a former Bergen County prosecutor himself, said the job was both complex and demanding, and that Musella will be up to the task.

“I know that Prosecutor Mark Musella will continue the great work being done at the BCPO, especially when it comes to community engagement and innovative ways to combat the opioid crisis, such as Operation Helping Hand,” Grewal said in a statement. “I also want to thank Prosecutor Dennis Calo, for serving the people of Bergen County for the last 17 months with dignity, professionalism, and grace.

“I look forward to working with Prosecutor Musella, and now First Assistant Prosecutor Calo to carry on the tradition of excellence that the people of Bergen County have come to expect from the BCPO,” added Grewal.

As Bergen County's chief law enforcement officer, Musella will oversee a staff of approximately 265 personnel consisting of assistant prosecutors, detectives, and support staff. He also exercises supervisory authority over approximately 2,700 sworn law enforcement officers in 72 law enforcement agencies operating in Bergen County.

In addition to conducting its own proactive investigations, the BCPO maintains specialized squads that assist municipal police departments in the investigation of crimes that include arson, homicide, sex crimes, drug trafficking, traditional organized crime, domestic violence, financial crimes, and cyber crimes.