A 36-year-old man of Rietvale in Modder River in the Northern Cape has been arrested for the rape and murder of his 51-year-old biological mother.According to police spokesperson Brigadier Mohale Ramatseba, it is alleged that the suspect and his mother were drinking wine together under a tree on Sunday night in Rietvale."It is alleged the suspect raped her mother and was caught in the act by a passer-by who raised the alarm. Police were alerted and unfortunately the victim was found dead."READ | Sisters sent to shop, return to find mom and brothers hanging from raftersThe man was later arrested."Post-mortem results conducted on Tuesday revealed that the victim was strangled."The man is expected to appear before the Modder River Periodical Court on Wednesday facing charges of rape and murder.The Kimberley Family Violence, Child Protection and Sexual Offences Unit is conducting the investigation.