An 18-year-old man has been arrested after he allegedly used a gun to carjack a woman and her six-month-old baby in Parramatta.

Police caught up with the man on Monday and initiated a pursuit across Sydney’s south-west that ended in a shopping centre.

It will be alleged by police a 33-year-old woman was sitting with her baby in the back seat of her car at a shopping centre on Church Street, Parramatta, about 4.30pm on Friday.

The man allegedly threatened her with a firearm and demanded she get out of the car, which she did.

The woman and baby were not injured.

Following investigations, officers tried and failed to stop a blue Suzuki on Hoxton Park Road, Green Valley, soon after 9am on Monday.

A pursuit through surrounding suburbs was terminated, but PolAir observed the vehicle entering the carpark of a shopping centre on George Street, Liverpool.

Police established a perimeter around the centre and tactical support including a dog unit was called in to help.

The man was chased on foot through various shops and “service ways” in the centre before being arrested.

As of Monday night the man was under police guard in Liverpool Hospital where he was being treated for an injured hand.

Charges including carjacking are expected to be laid against the man.