Police would not confirm whether the 22-year-old man being questioned matched surveillance photos of the suspect.
The Guardian Angels planned to patrol the Western Blue Line stop on the O'Hare branch Wednesday morning.
A 28-year-old working mother says a robber grabbed her phone as their Blue Line train stopped at the Western station at 1909 N. Western Ave. Police say it is the second such robbery at the stop in recent weeks.
She ran after the thief, but was stopped short when she fell. The incident left Gabrielle McCaulley with a broken ankle, and her young daughter with a deeper pain.
"We were just on the couch just crying because she was hurt. And that's the first time seeing my mommy hurt," said Asia Austin, robbery victim's daughter.
It happened around 6 a.m. Sunday morning when McCaulley was alone on the Blue Line headed to her job at a Northwest Side nursing home. McCaulley was texting a relative on her new Samsung Galaxy Note 3 smart phone as the doors of the train opened at the Western stop.
"That one second I had that phone out, that's all it took is one second. And he took it," said McCaulley.
McCaulley says she chased the man off the train and down the stairs. Her fingers grasped at the back of his black hoodie when she fell, she said.
"I was yelling like, 'Help! Help! Help! He's taking my stuff!' And I was just yelling really, really loud, 'Help me! Help me! Help me!'" said McCaulley.
"My Auntie Tyra, she told me that something happened to my mommy. And I thought she died. And I didn't want to lose my momma because without my momma I wouldn't be here," said Austin.
Police say it was the second robbery at the Western Blue Line stop this year. A 32-year-old woman was robbed on the train in similar fashion on January 6 around the same hour of the morning. McCaulley has a message for fellow riders.
"I know we're bored on that train sometimes. We want to pull that phone out. Get a book. Read a book. Please don't pull out your device," said McCaulley.
Police have only a vague description of the suspect, but they are looking at surveillance video. He is described as a medium-to-dark-complected black man between 20 and 25, standing 5-foot-6 to 6 feet, and weighing 150-200 pounds.
Because of her injury, McCaulley is unable to work for the next six weeks, so she's lost more than just her phone.
Anyone with information should contact Area North detectives at (312) 744-8263.