Emergency crews were called to the cosmetics section in the Myer store at 10.30am on Monday following reports of an attack.

Police said they found the body of a man inside the shopping centre. Another man was arrested and taken to Parramatta police station where he is assisting with inquiries.

Shopping centre employees said they heard two women screaming: "He's killing him! He's killing him!"

Myer employee Bianca Zoratto-Ivanov said a friend of hers saw the stabbing close to the entrance of the store's cosmetic section.

"He heard a scream, like a man yell," she said. "He heard it again and then he heard two young women scream: 'He's killing him! He's killing him.'

"That's when he turned around and saw the incident was taking place. He saw the man facing the store and doing the stabbing motions."

Ms Zoratto-Ivanov said she knew the employee at Aquila Shoes who had seen the offender drive a machete into the victim.

"The man had a big machete," she said.

"He saw glimpses of it, but turned around as soon as he saw.

"It wasn't in Myer, it was outside of Myer."

She said a number of women from the cosmetics section of Myer also saw the bloody stabbing and they were heard screaming.

Police have established a crime scene and investigations into the circumstances of the man’s death are in the early stages.

Witnesses say there is a large police presence with parts of the centre closed.

A witness told Macquarie Radio that a man started stabbing another man. He then lit a cigarette, took his shirt off and waited for police to arrive.

The man, who had a large tattoo across his back, was arrested a short time later, the witness said.

Confused and frightened shoppers were herded out of Myer, which has now been blocked off with tape on every level.

Police and Westfield staff are manning the blocked off areas, directing shoppers to the car park.

- with Emma Partridge