Two St John Ambulance paramedics remain off duty after they were assaulted at a Merriwa service station on Saturday night.
Clarkson detectives said the men were refuelling their ambulance at the BP Connect on Hester Avenue about 11pm when they noticed a man throw rubbish on the ground.
The man became aggressive when the paramedics asked him to pick up the discarded item, attacking them and punching both in the face.
One of the ambulance officers received a cut to his left ear and the other had swelling above his right eye, a grazed head and a sore mouth.
The pair went to Joondalup Health Campus and had to be stood down from duties for the remainder of their shift. They are likely to return to work later this week.
St John metro ambulance general manager James Sherriff said it was disappointing people working in the community to save lives were attacked in this fashion.
Police are investigating the incident. Anyone with information should call Crime Stoppers on 1800 333 000.