Police have shot and killed a man after responding to a reported brawl at a major shopping centre in Sydney’s west.

Emergency services were called to the Westfield Mount Druitt carpark on Saturday afternoon following reports of a fight between two groups.

When officers arrived, a man armed with a machete reportedly approached them, prompting police to fire “a number of shots.”

A NSW Police spokesperson confirmed a firearm was discharged during the incident.

The man, believed to be in his 20s, was treated by paramedics but died at the scene.

Criminal defence lawyer Rick Rabbah, who was at the scene, told 7NEWS the incident was distressing, even for someone in his profession.

“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 critical incident team from State Crime Command’s Homicide Squad will lead the investigation into the circumstances surrounding the incident.