Police say the couple were walking to the Chifley Shops around 7pm with their child in a pram when they were approached from behind by a boy who threatened them with a rock and demanded money.
The boy then struck the 34-year-old male victim on the face with the rock, and threatened the woman and her baby.
The victim handed over a small sum of cash, and the offender fled back into the underpass in the direction of Lyons.
The boy was described as fair-skinned, with a thin build, 165—168cm (5’5” to 5’6”) tall and wearing a T-shirt and shorts.
Police say a short time later a 14-year-old boy whose appearance was similar to the description provided was questioned, details were taken, and he was released into the care of a responsible adult pending further police enquiries.
Police ask anyone who knows anything about the incident to contact Crime Stoppers on 1800 333 000 or atwww.act.crimestoppers.com.au.