NEW YORK — A man was arrested and charged with murder Thursday in connection with the fatal stabbing this week of an activist in Brooklyn, the New York City Police Department said.

The victim, Ryan Carson, 32, who grew up in Massachusetts and graduated from Cardinal Spellman High School in Brockton, was stabbed repeatedly shortly before 4 a.m. Monday in Bedford-Stuyvesant, police said. When officers arrived, they found Carson lying on the sidewalk, unresponsive, with stab wounds to his chest. He was taken to Kings County Hospital, where he died.

The man who was arrested, Brian Dowling, 18, of Brooklyn, was charged with murder and criminal possession of a weapon.

Video footage of the killing showed Carson being attacked by a man who had walked past him and his girlfriend on the street seconds earlier. The man appeared agitated and had begun knocking over scooters on the sidewalk before the couple walked toward him.

Carson, a campaign manager for the New York Public Interest Research Group, was a community organizer and poet who also ran NO O.D. N.Y., a campaign to end drug overdose deaths.

“Ryan Carson threw himself into everything he did with passion and humanity,” Sen. Chuck Schumer, D-N.Y., a Brooklyn resident and the Senate majority leader, wrote on X, the platform formerly known as Twitter.

“I worked with him on a big town hall he hosted with NYPIRG and on the Inflation Reduction Act,” Schumer wrote. “A rising talent and an extraordinary activist. May his memory and work inspire us.”

Through video and witness interviews, detectives determined that Carson and his girlfriend were sitting on a bus stop bench at 3:47 a.m. when a man walked by, Joseph Kenny, the Police Department’s chief of detectives, said at a news conference Wednesday.

At first, the man and the couple did not interact, Kenny said.

However, after the man had walked about 40 feet away, he stopped and began kicking and damaging mopeds parked on the sidewalk. The couple stood up and began walking toward him, Kenny said. Suddenly, the man turned toward the couple and asked Carson, “What are you looking at?”

“Mr. Carson immediately tries to de-escalate the situation,” Kenny said. “This male then produces a knife and swings it at Mr. Carson, who begins to back up. Mr. Carson eventually trips and falls to the ground. The unidentified male then stabs Mr. Carson three times, striking him once in the right chest.”

One of the stab wounds pierced Carson’s heart, police said, causing his death.

As Carson lay on the sidewalk, the man stayed briefly at the scene, kicking him and threatening the woman, Kenny said. Shortly after, a woman — who appeared to know the assailant — appeared at the scene, apologizing to the couple and calling the attacker by a name, he said.

Before the stabbing, the attacker was seen on the corner with the woman, whom the police believe to be his girlfriend, “acting very agitated,” Kenny said.

A vigil held for Carson in Brooklyn on Monday evening drew a crowd of more than 100 people, according to reports.

Local leaders hailed Carson’s work as an activist. Jumaane Williams, the New York City public advocate, described him as “a friend, mentor and ally” and said he was “devastated” by the killing.

“I’m horrified to learn of the brutal murder of advocate Ryan Carson in Brooklyn today,” Chi Ossé, a City Council member who represents Bedford-Stuyvesant and Crown Heights, said on X. “This tireless defender of his neighbors was stolen from us.”

In a 2020 interview with Line Rider Press, which describes itself as a poetry website and book publisher, Carson said he was drawn to both poetry and community organizing as a college student at the Pratt Institute, where he enrolled at around the same time as the start of the Occupy Wall Street movement.

“The two new passions informed each other and most of my art since has been focused on locating the individual in collective struggle,” said Carson, who published several poetry collections and zines.

“My own writing is a means of decompressing,” he said. He later added: “For me, poetry is a moment of reflection before going back to work.”

This article originally appeared in The New York Times.