CHICAGO (CBS) — A 15-year-old boy was charged Thursday with two robberies on CTA trains in the downtown area this week.A 15-year-old boy was charged Thursday with two robberies on CTA trains in the downtown area this week.

Authorities said he stabbed the victim during one of the robberies, and attacked a bystander during the other.

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The boy was charged with two felony counts of armed robbery with a dangerous weapon, and as well as aggravated battery and assault to a transit employee.

Police said on Monday, a 23-year-old man was on a train near the Adams/Wabash station in the Loop when the teen robbed him at knifepoint and stabbed him.

The victim was taken to Northwestern Memorial Hospital in good condition, police said.

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The following day, the suspect robbed a 29-year-old woman on a train in the 300 block of North Wells Street – near the Merchandise Mart station, police said. He also assaulted a 51-year-old man with a knife and demanded that the man not interfere.

Police did not specify whether this man was a transit employee, as the charges may suggest.

Detectives found the teen through video surveillance and through a community alert, and he was arrested at the Wentworth (2nd) District police station at 51st Street and Wentworth Avenue, police said.

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The boy is due in Juvenile Court on Friday.

CBS 2 Chicago Staff