Police investigating two shootings and one stabbing in Sydney's west

Police are investigating a possible case of mistaken identity which led to a drive-by shooting in Sydney overnight.

The shooting was one of a series of violent crimes to occur in Sydney's western suburbs since yesterday.

About 3pm on Friday, police and emergency services were called to Betty Cuthbert Avenue in Ermington, following reports a man had been stabbed.

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A 30-year-old man was found with a single stab wound to the abdomen and was taken to Westmead Hospital in a serious but stable condition.

Three hours later, around 6.30pm, investigators were informed the man's younger brother, a 28-year-old, had admitted himself to Westmead Hospital with a gunshot wound to his right thigh.

The injury is not considered life threatening.

Investigators believe the two incidents are linked.

Then, about 10.10pm, police were called to a third incident in Merrylands, following reports of another shooting.

Police arrived to find a bullet hole in a back room of a house house on Lockwood Street.

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The five occupants of the house, who were inside at the time, were not injured.

Police have been told a vehicle was seen driving slowly along the residential street, before a number of rounds were fired.

The vehicle, described as a black 4WD or hatchback, then drove quickly from the scene.

Police believe that the shooting is a case of mistaken identity.

Police have not said if they consider the drive-by shooting to be connected to the other acts of violence.