Police allege Jason Stefanski (23) was in a violent argument with his 69-year-old father at the front of their Justicia Close home when he attacked Bill Butler (68), who had reportedly attempted to intervene.
Ambulance crews rushed Mr Butler and the accused’s father to Joondalup Health Campus after being called to the home about 1.20pm.
Mr Butler died in hospital. Mr Stefanski’s father was taken to Royal Perth Hospital in a critical condition. He died yesterday evening.
The accused man was treated for minor injuries in Royal Perth Hospital.
He is expected to face Stirling Gardens Magistrates Court on two charges of murder tomorrow.