Winfield allegedly followed the woman from the Bryn Mawr station. | Wikicommons, Cook County Sheriff

A south suburban man used his phone to film a woman’s underwear on the Red Line, then followed her from the train and robbed her in Edgewater, police said.

48-year-old Reginald Winfield of Harvey is charged with robbery and videotaping through clothes.

An Edgewater woman told police that Winfield approached her near the Bryn Mawr Red Line station around 11:45 p.m. on August 6 and said, “I’ll whoop your ass and take your phone” before snatching her iPhone from her hands and running away around.

Cops caught up with Winfield nearby, and the 31-year-old victim identified him for police.

An investigation revealed that Winfield had been videotaping the woman on a CTA train before he robbed her, police said. Officers found evidence that Winfield “was trying to videotape the victim’s underwear” on the Red Line.

A judge set Winfield’s bail at $90,000.