The ju-jitsu specialist and cage fighter was asleep in his Hunter Valley home when the harrowing noises emanated from a nearby car park early on Tuesday.

"I haven't really heard screams like that before; they were pretty awful," he said.

He jumped out of bed, still in his gear from training the previous night, and ran outside only to be threatened by two men before they ran away.

Mr Grayson, 27, thought they had broken into his car and stolen his work laptop.

In fact, he had helped foil what police allege was a vicious armed robbery of a woman who was punched in the face at least six times and threatened with a weapon.

He chased the men with the help of a council worker who had also come across the alleged robbery.

The suspects ran into a one-way street with the martial arts expert in pursuit.

He tackled one suspect to the ground and grabbed at the second, taking a handful of his pants, which ripped, allowing the man to escape.

"I am just a bit filthy that I didn't get the second one; I should have got him," Mr Grayson said.

With the first suspect in a martial arts hold, Mr Grayson, whose first cage fight is in next few months, waited for the police.

Police said the victim, 40, had parked in the car park in Moore Street, Maitland, about 5.30am on her way to gym class.

She saw two men and waited a short time for them to leave before opening her door.

Police say it was then that she was set upon by one of the men, who threatened to stab her and punched her repeatedly in the face before stealing her bag.

She tried to kick back and screamed.

"If he had not have turned up, who knows what could have happened?" Detective Inspector Mitch Dubovski said.

CCTV shows the men getting off an XPT service at Maitland train station about 4am.

A Casino man, 24, has been charged with aggravated robbery.

A second suspect, wearing dark clothing in the railway station footage, is still on the run.

Newcastle Herald