A second suspect in the stray-bullet killing of a seven-month-old baby on a Brooklyn street was arrested on Friday, investigators said, two days after a shooting the New York police department (NYPD) commissioner called “a tragedy that truly shocks the conscience”.

Matthew Rodriguez, 18, was apprehended in Pennsylvania by NYPD detectives working with US marshals, according to authorities.

The suspected shooter, 21-year-old Amuri Greene, was arrested shortly after the drive-by gunfire that killed Kaori Patterson-Moore. Greene pleaded not guilty to murder and other charges at an arraignment on Friday night.

Kaori was in her stroller when two men sped down a street on a moped on Wednesday afternoon. Greene, riding on the back of the vehicle, fired into a group of people on a street corner, according to a court complaint.

Kaori’s mother, Lianna Charles-Moore, told the New York Post that after hearing what she initially believed were fireworks, she was comforting her startled two-year-old son – who had been grazed by a bullet – when she looked to her left and saw her baby daughter bleeding. The infant had been shot in the head.

“My daughter was innocent. She didn’t deserve that,” Charles-Moore told the newspaper. She said her daughter was just about starting to crawl and had recently begun saying “Mama”.

Research by gun control advocacy group Everytown for Gun Safety has established that firearms are the leading cause of death for children and teens in the US. Nonetheless, Congress over the years has been unable or unwilling to implement more substantial gun control in the US.

Greene told police he was aiming for another person in the crowd, according to the court complaint.

Police said the moped sped and crashed into a car two blocks away, hurling both men off the vehicle. Greene was injured and soon was hospitalized and in police custody, but the moped driver fled.

Authorities haven’t yet released court papers that detail Rodriguez’s alleged role. But they haven’t indicated they were looking for anyone other than the gunman – alleged to have been Greene – and the moped driver.

Greene was being held without bail after his arraignment. A voice message seeking comment was left with his attorney.

Police didn’t immediately have information on how the men are connected or where Rodriguez lives. No working telephone number for him could immediately be found.

Police charges against him were pending.

New York’s mayor, Zohran Mamdani, and police commissioner, Jessica Tisch, expressed heartbreak and outrage over Kaori’s death.

“This is a terrible day in our city, a tragedy that truly shocks the conscience,” Tisch said at a news briefing on Wednesday.