Mandurah Detectives are investigating an incident that occurred on Gordon Road, Meadow Springs on Tuesday.
A man was at a park near Gordon Road when he was observed by a member of public committing an indecent act.
When the man realized he had been seen, he left the area.
Detectives would like to speak with anyone that may have seen the incident, in particular, a member of public that was riding a pushbike in the area.
This man was travelling easterly on Oakmont Avenue
Anyone with any information is asked to contact Crime Stoppers on 1800 333 000 or report online at crimestopperswa.com.au.