The Boston Police Area B-3 district welcomed a new commander in late October. Capt. Sean McCarthy, who replaced Capt. John Flynn, since then has been making the rounds to introduce himself at civic association meetings, including last week’s Codman Square Neighborhood Council (CSNC).
The B-3 district encompasses the western side of Dorchester– with Washington Street as the dividing line— and all of Mattapan. He arrives at his command with crime at near-historic lows citywide, but recently trending in the wrong direction in B-3, where crime is up 15 percent through Nov. 30 compared to last year. Homicides have jumped from 4 in 2024 to 8 in 2025, and notable increases in domestic and non-domestic aggravated assaults, as well as street robberies and car thefts, have also been recorded.
Capt. Sean McCarthy, commander of the B-3 police district. Seth Daniel photo
McCarthy had been an administrative lieutenant in the downtown A-1 district for the past eight years. He started his career as a patrolman 27 years ago at the adjacent C-11 district, which encompasses most of eastern Dorchester. In his early career, he served alongside the current C-11 commander, Capt. Steve Sweeney.
“I was in C-11 for several years and was with Capt. Sweeney at C-11 back then,” McCarthy told the CSNC membership last week. “Our working relationship is really solid. here’s not many things we’ll miss between the two districts.”
He and Sweeney, who was at the meeting, both mentioned, for example, a recent shooting incident that started in B-3 on Southern Avenue on Nov. 19 where a scooter operator fled the scene, crossing police district lines into C-11. Officers and leadership in both districts worked together to stop the scooter on Waldeck Street and take a juvenile male into custody on Dakota Street.
McCarthy said he is impressed with the community involvement in B-3. He noted that the district is much safer than it was in the past, though he cited more work to be done.
“It’s a very safe area right now, no question, it’s a statistical fact,” he said, “in relation to crime 10 to 15 years ago when it was not as safe. Community involvement is super-high now. I’m amazed at all the community groups and I’m excited to get out and learn the community concerns…A-1 downtown is definitely a different landscape than B-3, which is more residential with different types of crimes.”
McCarthy and the B-3 district will host a Community CompStat meeting in person on Jan. 29 at 10 a.m. in the Mildred Avenue Community Center. It will mark the first time that B-3 has hosted such a meeting, which was done in C-11 the last two years.The meetings go over crime trends in depth and seek community input to help police strategize and determine their allocation of assets.
