His name and age were not immediately released.
Homicide detectives were processing the crime scene and no arrests had been made as of Wednesday night, Watson said.
The boy’s death is the city’s 17th homicide this year, compared with 23 on July 24, 2021, Watson said.
In a press conference at the scene, Mayor Michelle Wu lamented the loss of a young life to gunfire.
“Anytime there’s an incident of gun violence in our community it’s absolutely unacceptable,” Wu said, according to a recording of the news conference. “And when we see the loss of life, especially of a young child, we are all robbed of the potential, the life that this young man had ahead of him.”
Wu said trauma teams are on site to support community members.
Suffolk District Attorney Kevin Hayden urged anyone who knows what happened to come forward to police.
“One homicide in our city is one too many,” he said at the press conference. “They’re all tragic, but when it happens to someone at a tender age, when it happens to a young teenager, it obviously cuts right to the heart and the very fabric of our communities and our children.”
District 4 City Councilman Brian Worrell recalled growing up in the neighborhood and going to nearby Franklin Park.
“We have to stop the violence in our streets,” he said at the press conference. “And it’s going to take all of us, all of us here in the city of Boston to make sure that we come together as a community to end gun violence.”
At 11:00 p.m., Ellington Street, lined with triple deckers and police cars, was quiet.
Ellington Street was quiet Wednesday night as police continued to investigate the fatal shooting of a teenager. Camilo Fonseca
A handful of police officers continued to collect evidence near where the teenager was shot, scouring the ground with flashlights. A police photographer took pictures of a playground at the intersection of Erie and Ellington streets.
Across the street, two convenience store workers sat on the steps of the Erie St Market watching in silence.
Alexander Thompson can be reached at alexander.thompson@globe.com. Follow him on Twitter @AlMThompson You can contact Camilo Fonseca at camilo.fonseca@globe.com. Follow him on Twitter @fonseca_esq.