NEW ORLEANS -- Flashing police lights and crime-scene tape are common sights in some parts of Baltimore, the deadliest big city in the United States with 309 homicides last year. They are also regular sights in many New Orleans neighborhoods.

NOPD Superintendent Michael Harrison won praise in recent weeks when the city marked its lowest homicide rate in four decades. Results like that made him an attractive candidate to become Baltimore’s next police commissioner.

RELATED: Violent crime in New Orleans is at the lowest rate since the 1970s

“He understands the similarities between us and New Orleans,” Baltimore Mayor Catherine Pugh said Tuesday while addressing the surprise announcement that Harrison was leaving the Crescent City for Charm City.

A month earlier, after reports surfaced that Harrison was being courted for the Baltimore police commissioner job, he shot them down, saying he was happy in New Orleans. But on Monday, Pugh announced that her first choice, Fort Worth Police Chief Joel Fitzgerald, withdrew from consideration after his child suffered a medical emergency late last week.

On top of the stubborn crime problem, Baltimore faces a new challenge that Harrison is familiar with: a police department operating under a federal consent decree.

Former NOPD Superintendent Ronal Serpas, under whom the Police Department began operating under a consent decree, said Harrison has his work cut out for him but is the right person for the job, considering his experience in New Orleans and working alongside the feds.

“When a city has a consent decree like Mike is going to confront, a lot of changes are already underway and in place, and it's going to be your job to make sure you carry them to fruition and create new ones,” Serpas said. “That'll be a benefit for a chief going into a consent decree city. A lot of the big fights will already be had, if you will.”

RELATED: Michael Harrison to leave NOPD to lead Baltimore police

One area that might require a learning curve for Harrison is Baltimore’s powerful police union. Serpas said that will be new politics Harrison will have to learn, but he’s confident he’s up to that challenge as well.

Baltimore City Fraternal Order of Police Lodge 3 did not respond to requests for comment on Tuesday. But on Monday, the FOP issued a statement that asked for Pugh to hire not only the best candidate but to then let him or her operate the department with “the appropriate autonomy.”

“In essence, we hope that she finds a practiced leader and then allows him or her to lead us to be not only a better police department but a better city,” the statement reads in part.

While Pugh is confident in Harrison, Baltimore City Council President Bernard “Jack” Young asked in a letter to the mayor that Harrison describe his “connections to and knowledge of Baltimore City’s communities.”

That outsider status, though could be beneficial, said state Sen. Bill Ferguson (D-Baltimore).

“We need some fresh eyes. We need somebody that can come in, that has experience implementing a consent decree and can really take a look top to bottom at our department,” Ferguson said.

Mayor LaToya Cantrell's office has not announced who will replace Harrison, at least on an interim basis, when he leaves or a timeline for a search for his replacement.