A CAR breakdown on the Kwinana Freeway today sparked a horrific chain of events that resulted in the death of a motorcyclist.

It has been a horror day on Perth roads, with a cyclist killed in Rockingham just a few hours earlier.

Police and emergency services were called to the crash on Kwinana Freeway southbound, near the South Street exit in Bull Creek, just before 9.30am.

Two cars collided and one of them hit a motorcyclist.

At 9.23am a car was parked in the right hand side of the freeway southbound, near the South Street exit.

A traffic officer on a police motorbike pulled up adjacent to the motorist to talk with the driver.

Shortly after, a second vehicle – a Toyota ute travelling southbound – collided with the parked vehicle, which led to another collision with a motorcyclist also travelling southbound.

The male motorcyclist was flung off his machine and suffered fatal injuries.

The parked car had broken down and its driver and the traffic cop were “shaken” after witnessing the fatality and trying in vain to save the rider, acting superintendent Ian Clarke said.

Major Crash officers spent the morning at the scene conducting further inquiries.

Police Internal Affairs officers were also in attendance – a standard procedure as a police officer was present at the time of the crash.

Main Roads officials assisted with traffic management and several road diversions were in place.

Motorists were advised to take alternative routes as southbound lanes were closed for most of the day.

The crash site has now been cleared and the lanes were reopened this afternoon.

Earlier, a cyclist was killed after a collision with a vehicle about 6.10am at Ennis Avenue and Patterson Road, Rockingham.

The rider was taken to Rockingham Hospital, however at 9.30am police confirmed the man had died. Major Crash detectives will also investigate that fatality.