The hold-ups have happened in the 2000-block of North Richmond Street just before 10:40 p.m. and in the 1700-block of North Wolcott Avenue about 11:40 p.m. last Wednesday and in the 2700-block of West Fullerton Avenue just before 5:30 p.m. Friday.
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The suspects approach the victims, point a gun at them or at the back of the victim's head and demand their personal belongings, CPD said.
They were seen getting into a possible gray Ford Escape and are described as 16 to 25 years old; 5-feet, 7-inches to 5-feet, 10-inches tall; 130 to 150 pounds and wearing dark or all black clothing, police said.