'Violent' Man On The Run After Fatal Stabbing At Construction Site

A man "capable of a violent act" is on the run, after a man died and his son was left fighting for life following a stabbing in Sydney's inner-west.

Police were called to the Princes Highway at St Peters about 1pm on Wednesday following reports two men had been stabbed at a construction site.

Albert Metlege, the 76-year-old manager of the site, was found dead at the scene. Despite the urgent work of paramedics, he could not be revived.

His son Antony, 33, was treated at the scene after being found with stab wounds. He was taken to Royal Prince Alfred Hospital in a critical condition, where he was taken into surgery to treat his injuries.

A large-scale search is underway for a third man, aged 49, who police were told fled the scene wearing high-vis work gear.

"We believe he is capable of a violent act," Police Inspector Chad Deegenaars told reporters at the scene.

Police have set up a crime scene at St Peters. Image: 10 News First

The person believed to be behind the stabbing is is thought to be known to the victims. Police believe the man was also working at the construction site.

He was last seen in the nearby suburb of Rockdale, five kilometres south of the crime scene. Deegenaars said it is believed the man "hitched a ride", but it is unclear how, or with who.

Police have secured the weapon thought to have been used in the stabbing, but have warned members of the public not to approach the man if they see him.

"Investigators are finding out what the disagreement was, what the motive was."

The man who fled the scene is described as being of Caucasian appearance, about 180cm tall, with a large build and a shaved head.

He was last seen wearing a high-vis yellow shirt, long blue work pants and brown work boots. Deegenaars said it is believed the man may now be wearing a blue shirt, and possibly carrying a construction helmet.

Police inspector Chad Deegenaars. Image: 10 News First

A heavy police presence quickly assembled at the scene, where riot squad police are seen wearing bullet proof vests.

One worker at the site called the deceased Albert "a top bloke, best bloke".

"Good people," another worker said of the father and son.

Police are urging the public not to approach the man, but to call Triple Zero immediately.

Anyone with information about the incident is urged to contact Crime Stoppers on 1800 333 000 or online.