Homicide squad investigating 'critical incident' just north of Perth

Homicide detectives and the WA Police internal affairs unit are investigating a "critical incident" that happened on Friday morning just north of Perth.

Police and St John Ambulance were called to a house on Yosemite Loop in Ballajura just after 6am.

Officers found a man at the residence behaving erratically.

While he was being removed from the property the man stopped breathing, prompting first aid responses by officers who performed CPR.

The man was taken to Royal Perth Hospital where he is in a critical condition.

Anyone with information regarding this incident, or who saw or heard anything suspicious in the Yosemite Loop area between 5.30am and 6am on Friday morning is asked to call Crime Stoppers on 1800 333 000 or report the information online at www.crimestopperswa.com.au.