The first incident took place about 4.30am on July 22, when emergency services were called to a café blaze in Haldon Street in Lakemba.
No-one was injured and firefighters were able to control the blaze.
Police established a crime scene and the fire was treated as suspicious following reports men were seen fleeing the area.
The fire is believed to be linked to organised crime.
Witnesses told police a group of men wearing face masks and carrying pistols forced their way into a home and threatened a woman, aged 50, and two young girls, aged eight and 10.
The perpetrators allegedly took cash and jewellery and no one was injured.
Earlier this month, police established the same group of men were responsible for both incidents.
Strike force detectives, along with Raptor Squad and Tactical Operation Unit, then executed multiple search warrants across Guildford, Greenacre and Bankstown about 6am on September 12.
The three men were arrested and charged with several offences including special aggravated break and enter with intent armed with a dangerous weapon and robbery.
One of the men, aged 23, was charged with destroying property with fire and the 20-year-old was charged with driving a car with a disqualified licence.
The three men were refused bail after appearing in court.
A fourth man, aged 27, was arrested and extradited from South Australia to Sydney on September 13.
He was charged with break and enter with intent armed with a dangerous weapon, robbery and participating in a criminal group contributing to criminal activity.
The man was refused bail and appeared in court on September 14.
Police allege the men worked together during the crimes as part of an organised crime network.
“What we are seeing in Sydney is that organised crime networks are parcelling out jobs to these smaller crews in order to keep themselves clean,” said Detective Superintendent Gordon Arbinj, Commander of the SCC Financial Crime Squad.
“My message is simple. To anyone considering working for criminal syndicates – don’t. Our officers are tirelessly working around the clock to identify you and bring you before the courts.”
Detective Superintendent Joseph Doueihi assured the public that police will hunt down crime groups causing terror in Sydney.
“No one should feel afraid or be threatened in their own home, especially young children. While these attacks were targeted, I want the public to know that we will not stop in pursuing these criminals who feel it is their right to commit these crimes,” he said.
“For those small-time groups who engage in these needless violent crimes on behalf of other criminals, know you are facing the full might of the NSW Police Force.”
Investigations continue and police expect more arrests will be made.