Man gunned down outside Sydney home believed to be former Nomads bikie

A man shot dead while he put his bins out in Sydney’s west last night is believed to be a former Nomads bikie.

Adrian Buxton, 32, was shot in the head while he stood on a nature strip in the quiet cul-de-sac Coral Pea Court in Colyton about 9pm.

His wife and young son were just metres away, inside their home.

Witnesses told police they saw two hooded men flee the scene, one of whom allegedly pointed a weapon at a shocked neighbour.

Paramedics treated Mr Buxton, but he died at the scene.

He was known to police and investigators do not believe it was a random attack.

A neighbour told 9NEWS he had heard loud bangs.

"I heard what I thought were firecrackers going off and then I heard some commotion, checked out the window and saw some guys running off," he said.

Police established a crime scene and searched the surrounding area.

Anyone with information is urged to contact Crime Stoppers on 1800 333 000.