The murder was the first killing on the subway in more than a year.
Chief of Detectives Dermot Shea said the killing stemmed from a feud between rival Central American gangs in Queens.
The victim, Abel Mosso, 20, had been identified by investigators as a member of the 18th Street gang, he said. The gunman is a known MS-13 gang member, Shea said.
Though Shea did not name him, the man taken into custody was Ramiro Gutierrez, a law enforcement official said, speaking on the condition of anonymity to discuss an open case. Gutierrez and 11 others were charged in December by the Queens district attorney with conspiracy and attempted murder, as well as drug and weapons charges. He was freed on $2,500 bail awaiting trial.
Gutierrez was being questioned by detectives Monday evening. The district attorney had yet to file charges against him in Sunday’s killing.
The shooting, which was caught on video by a bystander, occurred around 12:45 p.m. Sunday. A fight broke out on a crowded 7 train bound for Manhattan and spilled out onto the platform at the 90th Street-Elmhurst Avenue station in Elmhurst.
In the video footage, three men can be seen wrestling on the ground. One man gets to his feet and points what appears to be a small revolver at Mosso. Five to six shots ring out, as bystanders scream and run for cover.
Mosso was shot several times in the face and died at the scene, police said.
Photographs of a man resembling Gutierrez, taken from security cameras near the subway station, were circulated by police, and witnesses identified him to detectives. The gun was not found.
Police were still seeking a second man filmed by security cameras as he fled the subway station wearing a gray sweatshirt and covering his face with a scarf.
The rivalry between MS-13 and 18th Street goes back decades to their origins in Los Angeles. Both gangs later established criminal operations in Honduras, El Salvador and Guatemala, among other places. They view each other as mortal enemies.
MS-13 has been active in New York City and the surrounding region for over a decade, and remains a persistent threat despite several rounds of indictments by local and federal authorities. In December, five accused MS-13 members lured a 23-year-old man, Ian Cruz, to a bird sanctuary in Queens, where he was shot to death.
The 18th Street gang is a newer arrival to New York, but has begun to target its longtime rivals, police said. In May, the Queens district attorney indicted seven men accused of being 18th Street members in the murder of an MS-13 rival.
This article originally appeared in The New York Times.