Three people are in police custody in connection with last week’s shooting in the Bronx subway system that left one man dead, authorities said.

Police said 24-year-old Justin Herde, 38-year-old Betty Cotto and 42-year-old Alfredo Trinidad were taken into custody in connection with the incident Monday. It wasn't immediately clear what charges they face.

Investigators said the incident took place Friday morning just before 5 a.m.

According to police, one of the three suspects sat down next to 45-year-old William Alvarez while on board a southbound D train that was leaving the Fordham Road stop in Fordham Heights. The two exchanged words, and then a physical fight between the victim and the three suspects followed, police said.

At some point during the fight, Alvarez was wounded, police said. He was pronounced dead at St. Barnabas Hospital on Friday.

NYPD Chief of Transit Michael Kemper said on Sunday that the city’s medical examiner determined Alvarez died “by gunshot.”