Man accused of punching 92-year-old at Mandurah Forum to appear in court today

A 36-year-old man accused of punching an elderly man in the face at the Mandurah Forum will appear in court today.

The 92-year-old victim was getting out of his car in the car park of the shopping centre around 1.30pm on Tuesday when he was approached by Eddie Gaugnin.

Without warning, Gaugnin allegedly punched the victim in the head, knocking him to the ground.

When a bystander tried to intervene, it's alleged Guagnin threatened them with a box cutter.

The 36-year-old was arrested a short time later at a nearby house.

The victim, Graeme, told 7NEWS he nearly lost part of his ear in the attack and now needs assistance to walk.

"There was blood all over the place," he said.

Gaugnin has been charged with aggravated assault occasioning bodily harm and being armed in a way that may cause fear.

He will appear in the Perth Magistrates Court today.