A man has died following a shooting at a Western Sydney shopping centre.

Police were called to the rooftop carpark at Westfield Mount Druitt about 3.15pm on Saturday following reports of a brawl between two groups.

Police said a man approached officers wielding a machete, prompting them to fire “a number of shots”.

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The man, believed to be in his 20s, was shot in the abdomen and treated by paramedics at the scene.

Despite their efforts, he could not be saved and died shortly after 4pm, police said.

Scared crowds were seen trying to flee the shopping centre as the shooting unfolded, according to a shopper.

A witness reported seeing one person armed with a machete and another carrying a gun.

They said they hid in the laser tag area to avoid the armed individuals during the incident.

Another witness told 7NEWS they had seen someone running around with a machete.

The witness said police then “blocked him off near the cinema” before firing at least one shot.

Rick Rabbah, a criminal defence lawyer who was at the scene, told 7NEWS the incident was confronting, even for someone in his line of work.

“I specialise in criminal defence, but for things to occur for a day like 3pm on a busy weekend, it’s terrifying for everyone, even for someone like myself,” he said.

A crime scene has been established and an investigation into the circumstances of the incident is ongoing.