A young boy and an elderly woman are fighting for life after a horror multi-vehicle pileup on wet roads near Rockingham. A Transperth bus was stopped at a red light when as many as four cars slammed into its rear at the intersection of Dixon and Mandurah roads in East Rockingham about 3pm on Friday. The boy – believed to be six or seven years old – was being prepared to be medically evacuated to Perth Children’s Hospital from Rockingham Hospital via the RAC rescue helicopter. His injuries have been described as life-threatening. A woman in her 70s also suffered life-threatening injuries. She has been transported by paramedics to Royal Perth Hospital while a man in his 60s is being treated for non-life threatening but serious injuries. A Transperth spokesman has confirmed one of the agency’s buses was involved in Friday afternoon’s horror crash. The bus was in service and had passengers on board, but all escaped injury. It is understood the bus was stopped at a red light when the crash took place. The Kia the young boy was travelling is believed to have come to a stop behind the bus at the lights but was rear-end by another car, causing it to slam into the back of the bus. A third and fourth vehicle then hit the wreckage. Five St John WA ambulances were sent to the scene. Two, however, were stood down. Friday’s crash came shortly after St John WA warned the public of more ambulance delays as paramedics experience “extremely high” levels of demand. A public alert was issued across the Perth metropolitan region at 2.45 pm. “It is likely there will be a delay in an ambulance reaching people who call Triple Zero,” the alert read. As of Friday about 22 per cent of the St John fleet in the metropolitan area was ramped.