Heavily armed police arrested a 26-year-old man in Seven Hills late on Monday night and charged him with the murder of 15-year-old Brayden.

The charge comes a day after police appealed for public help to find a white car that was seen driving away from Brayden's street in Glenfield, in Sydney's south-west, about five minutes after the fatal shooting.

Brayden had been asleep in an upstairs bedroom of his family's house just after 6am on April 14 when a  masked intruder kicked down the front door of the house.

The male burst past Brayden's mother, threatening her with a pistol before storming upstairs to her son's bedroom.  The gunman shot Brayden twice in the head and then fled. 

Brayden was taken to Westmead Hospital, where he died several hours later. 

Brayden, who was known to police for local gang activity, would have turned 16 on Wednesday, an occasion his family is preparing to mark with deep sorrow. 

Three months into the murder investigation, and after reviewing hours of CCTV footage from around the area, police on Monday released images of a white car they were trying to find.

Homicide Squad Detective Chief Inspector Mark Henney said on Monday that police had tracked many vehicles in footage from cameras around Glenfield but only one fitted the timeframe around the shooting.

"This car arrives in the area about 15 minutes before the murder and is seen leaving the area less than five minutes after the murder," he said. 

About 11pm on Monday, heavily armed police arrested a 26-year-old man at an address in Dale Street in Seven Hills.

He was taken to Blacktown Police Station where he was charged with one count of murder.

He was refused police bail, and is due to appear in Blacktown Local Court on Tuesday.

Police said investigations into Brayden's death were continuing.

smh.com.au