What began as an ordinary Saturday morning commute in Brooklyn quickly unraveled into chaos — and for many riders, a renewed sense of vulnerability underground.

Shortly before 9 a.m., police say a man launched an unprovoked attack on two women waiting for an R train at the 53rd Street and Fourth Avenue station in Sunset Park. According to investigators, one of the victims, 51, was pushed from the platform onto the tracks. A second woman, 43, was punched in the face.

Both were transported to a hospital and listed in stable condition. Police sources said the woman forced onto the tracks suffered three fractured ribs, while the other sustained a split lip.

Commuters who witnessed the assault described a sudden eruption of violence. Without warning, a man pushed one woman onto the tracks and then turned on the other, striking her repeatedly. Bystanders rushed to help. A man and a woman yelled for the fallen rider to raise her hands, then pulled her back up onto the platform.

Police identified the suspect as Curtis Signal, 25. He was arrested later that day at a nearby shelter and charged with reckless endangerment, assault and harassment. Authorities say he is currently on probation through June 2027.

Law enforcement sources indicated Signal has prior arrests linked to incidents in the transit system. Among them: a September 2023 case in Queens in which he is accused of punching a 67-year-old woman waiting for an F train at the 169th Street station in Jamaica. According to police sources, the woman attempted to shield herself behind a pillar as Signal yelled and appeared agitated, but he allegedly struck her multiple times before fleeing. She sought help from a station booth attendant. He was not charged in that case until May 2024, when officers stopped him for fare evasion and connected him to the earlier assault.

Just days after the Queens assault, police sources said Signal was arrested again — this time accused of punching a police officer during a September 7, 2023 encounter at the Grand Concourse/Tremont Avenue station in the Bronx. That officer reportedly suffered a broken nose. In that case, he was charged with assault on a police officer, resisting arrest, disorderly conduct and obstruction of governmental administration.

Police sources also cited two earlier incidents: a December 1, 2022 attack at a Jamaica Avenue medical office in Queens in which he allegedly punched a 31-year-old woman and slammed her head to the floor, and a May 17, 2022 case in which he allegedly struck his 13-year-old sister at their Queens home, leaving her with a black eye. Charges in those cases included assault, harassment and acting in a manner injurious to a child.

For many riders, the latest violence feeds mounting anxiety about subway safety. Earlier this week, the first subway homicide of the year was reported when a man was shot and killed inside a Bronx station.