CHICAGO (CBS) — An arrest has been made in connection with a mob attack last month on a CTA Red Line train downtown.

As WBBM Newsradio’s Bob Conway reports, the attack happened around 10:30 p.m. June 9 on a Red Line train near the State-Lake subway stop.

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LISTEN: WBBM Newsradio’s Bob Conway reports

A 15-year-old boy was arrested in connection with the attack around 2 p.m. Monday, and was identified as the main assailant, police said. He was charged with felony robbery and aggravated battery, but his name was not released because of his age.

The victim of the attack was a 23-year-old man. The teen mob had just stolen the man’s 27-year-old female friend’s iPhone 4S. She had dropped the phone, and a teen had picked it up and taken it for himself.

The man told the teen to give his wife her iPhone back. But they instead began punching him in the face.

The group then fled the train at State and Lake streets, near the Chicago Theatre.

Another woman with the group, from West Chicago, told the Aurora Beacon-News it was the scariest night of her life.

She told the paper she and her two friends got on the Red Line at the Addison stop after attending the Brad Paisley concert at Wrigley Field. Near downtown, the group of teens got on, and by the time it was over, the man with the group had a broken bone near his eye and broken teeth, and he was bloodied.

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The couple called 911 at street level, and the woman tells the Beacon-News that police were slow to respond.

The Red Line incident was one of three high-profile attacks by teen mobs in the downtown area that same weekend.

Just before 10 p.m. on June 9, another teen mob attacked two men – one from Chicago, the other in town from Michigan – in the 500 block of North State Street. One victim was left with a broken jaw, the other suffered a cut lip.

In that case, the suspected muggers were apprehended quickly. They fled, but officers caught up with them on Kinzie Street between State Street and Wabash Avenue. Ten people were arrested.

One adult – 18-year-old Mitchell Coradarrowe, of the 5900 block of South Indiana Avenue – was charged with felony mob action and aggravated battery. Seven others, ages 13 to 16, were charged as juveniles with felony mob action.

In a third incident, a 36-year-old doctor from Northwestern Memorial Hospital was attacked by a teen mob as he walked home from work along Dewitt Place near Pearson Street in Streeterville early on June 10.

Police say the man was robbed and attacked by anywhere from 10 to 20 people. The man was taken to the hospital with a head injury, but he was able to walk on his own after the attack.

Police Supt. Garry McCarthy pointed out after the incidents that there were similar mob attacks last summer, and his department was able to get the problem under control. He said he believes they’ll be able to do it again this year, and it’s a matter of making sure his officers are where they’re supposed to be, to prevent these incidents from happening.

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The Sun-Times Media Wire contributed to this report.