Police said a 42-year-old woman was the alleged mastermind behind a string of robberies across western Sydney which targeted 39 businesses over three weeks allegedly involving her son and his friend.

The string of alleged attacks came to an end this morning when an 18-year-old armed with a hammer was filmed smashing in the front window of a Liquorland at Winmalee.

He was interrupted by a waiting police officer who chased after him. 

The masked offender allegedly ran straight to a waiting dark grey Suzuki Swift, where the 42-year-old woman was waiting for him.

They were both arrested and taken to Springwood Police Station.

It is alleged the woman orchestrated the string of robberies at businesses between Tuesday, May 13 and this morning at Winmalee.

Two people were seen smashing into a bakery at Caddens at about 1.30am on May 19 before the duo allegedly stole the till and left a mess of coffee cup lids behind them.

Outside the door a third person appears to be carrying another till that was allegedly stolen from a chicken shop next door.

Police also raided a unit at Blackett where a second 18-year-old man, believed to be the woman’s son, was arrested and taken to Mount Druitt Police Station.

“We’re talking of damage in excess of $150,000 and for local businesses that is a huge impact,” NSW Police detective superintendent Trent King said.

Charges are yet to be laid.