Police have released an image of a man they want to speak to over a fatal shooting in south-western Sydney yesterday.

Joshua George, 24, was fatally shot in the chest during a meeting at Gidley Crescent that appears to have been pre-arranged following a dispute on Saturday.

Detectives are looking for 21-year-old Graeme Smith, but they say he may be armed and dangerous and have warned members of the public not to approach him.

Smith is described as having a solid build, is between 170 centimetres and 175cm tall and has short, light brown or blond hair and brown eyes.

Anyone who sees him is urged to call triple-0 immediately.

The fatal shooting happened in the early afternoon while children were playing on the street.

Locals tried in vain to resuscitate Mr George and emergency services were called about 1:30pm (AEDT).

Mr George was taken to Campbelltown Hospital where he was pronounced dead.

Witnesses told police that the alleged gunman fled the scene through a neighbouring house and ran down the next street.

He is believed to have been a friend of the victim. Both men were known to police.

They say the shooting has no link to bikie gangs.

Detective Chief Inspector Mark Brett says police are hoping a man and a woman who were with the victim at the time of the shooting will come forward.

"There was an incident yesterday [and] it is a follow-on incident today," he said last night.

"The use of a firearm is a very serious offence and the death of a person as a result of that firearm is tragic.

"We are seeking assistance from two males and a female who were seen with the victim just prior to him being shot.

"We're doing everything we can to bring this to a quick resolution."

In a separate incident, a man was taken to hospital overnight with a wound to the leg after reports of gunfire at Auburn.