A man has been seen walking down a suburban street in Sydney's west carrying a rifle after the fourth shooting this week, with a bullet reportedly narrowly missing a baby's cot.

Police were called to Weigand Avenue, Bankstown, about 12.30am today after a resident heard gunshots.

Officers were also told a man was seen walking down nearby Carmen Street carrying a gun.

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But police said they had not found any sign of a shooting or the man until they were called by a Weigand Avenue resident who found a bullet hole in a bedroom window about 1.40am.

At the time of the shooting a woman and her four children, aged between two months and 10 years old, were in the bedroom.

Neighbours said the children's mother only realised a shooting had occurred when her nine-year-old son brought her the bullet casing, 2UE radio reported.

The shot narrowly missed a two-month-old baby's cot, the neighbours said.

None of the residents were injured.

Detectives from Bankstown police were continuing their investigation into the shooting and were hoping to hear from anyone who saw the man or heard anything suspicious before 12.30am.

Police asked anyone with information to phone Crime Stoppers on 1800 333 000.

It was the fourth shooting in Sydney this week.

It followed two drive-bys in Auburn and Arncliffe on Monday night, which might have been linked to drug dealing in the St George area, police said.

Those shootings were being investigated by the Middle Eastern Organised Crime Squad.

Yesterday morning, shots were fired in a shoot-out between two cars at an intersection in Greenfield Park.

Several bullets hit a nearby house, but no one was injured.

Director of the NSW Bureau of Crime Statistics and Research Don Weatherburn said the spate of recent shootings in Sydney was the worst he had seen in a decade.

"Some of these cases are before the courts, so I don't really want to go into the details, but there's no question that this is ultimately a dispute about a turf war, about organised crime and the proceeds from organised crime," Dr Weatherburn told ABC Radio.

"There's no doubt it's a degree of vengeance being taken on people for perceived misdeeds or actual misdeeds in the process.

"But whenever you get this heady mix of ready access to firearms and inability to take your illegal disputes to court to have them settled, you end up with this sort of problem."

Dr Weatherburn said he could not speculate about what type of organised crime was behind the shootings.

"It's one of those classic situations where, as I say, somebody is making substantial profit out of some form of illegal activity, somebody is trying to muscle in on the turf, you can't take the case to court so they resort to violence in order to settle a dispute."

He said it was hard to know how to deal with the problem, other than arresting and prosecuting the offenders, who could actually be part of a small group.

Dr Weatherburn said the "booming" amphetamine and cocaine markets might be a part of the disputes.

"I have no idea what's going on in the mind of those who are doing this sort of thing; no doubt there is a degree of intimidation.

"It really hardly matters ... it's only a matter of time before some innocent bystander is injured or killed in one of these incidents.

"The sad thing is that it's all taking place in just a couple of areas in Sydney, so the residents of those areas are obviously very distressed about it."

Canterbury, Bankstown, Fairfield and Liverpool were the main areas where shootings happened, he said.

He said a few years ago guns were stolen from a major store in South Australia, sold by dodgy gun dealers, while guns could also be imported illegally.

Recent shootings in Sydney:

January 11 - Shots were fired between two cars after some kind of altercation at an intersection in Greenfield Park, with several bullets hitting a nearby home.

January 9 - Shots were fired into a house on Marion Street, Auburn, about 9.45pm. Ten minutes later, shots were fired into a house on Fairview Street, Arncliffe. The Middle Eastern Organised Crime Squad was investigating whether the shootings were linked to drug dealing in the St George area.

January 4 - Lone Wolf bikie, Neal Todorovski, 37, was shot dead outside a Sans Souci apartment block.

January 1 - Matthew Hedges, a 25-year-old father of four, was shot in the chest and died, while two of his children slept beside him in Chester Hill.

December 5 - A father and his teenage son escaped injury after a shot was fired into a house in Mount Pritchard.

November 26 - Shots were fired on Charles Street, Petersham.

November 25 - Shots were fired at a house on Kingarth Street, Busby.

November 24 - Shots were fired at a house on Nash Street, South Penrith.

November 24 - Shots were fired at a business on Cleveland and Walker streets, Redfern.

November 10 - Shots were fired at a house on Nineveh Crescent, Greenfield Park.

November 6 - Shots were fired at a house on Stevens Street, Ermington.

October 27 - November 3 - Six drive-by shootings across Sydney's west, believed to involve the Hells Angels and Nomads gangs.

October 21 - Man dies after he was shot in the head inside a house in French Street, Maroubra.

October 18 - Shots were fired at a house on Walker Street, Turrella.

October 3 - Man was charged after allegedly shooting at another man on Pickwick Way, Ambarvale.

September 30 - Man was charged after an alleged drive-by shooting on Victoria Street, Botany.

September 29 - Police officers shot and killed a man outside Castle Hill police station.

September 26 - Teenager was shot by police in his home in Holmes Street, Colyton, following reported break-in.

September 26 - Man was charged with murder following the shooting death of man at Bonnyrigg the day before.

September 6 - Shots were fired at a house in Revesby in south-west Sydney.

September 6 - Shots were fired at a unit in Eden Street, Arncliffe.

September 5 - Man found in Bursill Street, Guildford, with a shotgun wound to his upper thigh.

August 30 - Up to a dozen shots were fired between two cars in Greenacre.

August 25 - Bullet holes were found in a car on Lackey Street, Merrylands.

August 24 - Bullets hit a house on Francis Street, Fairfield.

August 22 - Pizza shop was hit on Merrylands Road, Merrylands.

August 22 - Two men were shot in Barcom Street, Merrylands, in a domestic dispute.

August 23 - Bullets hit a house on Lachlan Street, Bossley Park.

August 21 - Bullets hit a house on Eddy Street, Merrylands West.

August 20 - Bullets hit a hairdressing salon on Harris Street, Fairfield.

August 19 - Bullets hit a house on Mallacoota Street, Wakeley, near Fairfield.