CHICAGO (CBS) — Police were asking for the public’s help Sunday night in finding a man who has been robbing people at gunpoint on and near the Magnificent Mile and in River North.

In each incident, the assailant came up and started chatting up the victim, and then implied or pulled a gun and announced a robbery. The assailant demanded property or cash from the victims and then ran off, police said.

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The incidents happened at the following times and locations:

• In the evening hours on Tuesday, Sept. 3, in the 200 block of East Pearson Street;

• In the early morning hours on Saturday, Sept. 7 in the 200 block of West Grand Avenue;

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• In the early morning hours on Tuesday, Sept. 10, in the 700 block of North Michigan Avenue.

The suspect is described as an African-American male between the ages of 25 and 35, standing 5 feet 9 to 6 feet 1 inch tall and weighing 160 to 180 pounds.

Police advise that people always be aware of their surroundings. Anyone who is confronted by an assailant is advised to remain calm, and also to remember any unique physical characteristics such as scars, tattoos, acne, or limps.

Police also advise never pursuing an assailant and calling police instead. If approached by a witness, people should ask for contact information.

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Anyone with information on the robberies is asked to call Area Central detectives at (312) 747-8380.