Western Cape police have confirmed that the deceased cop is 32-year-old Sea Point police constable Donay Phillips.
Two patients were also fatally wounded when a man allegedly grabbed the policeman's firearm and started firing shots.
Potelwa said an investigation into the circumstances surrounding the incident was under way.
She said reports from the scene indicate Sea Point police had taken a 35-year-old suspect to Somerset hospital for medical attention when a man in the ward grabbed the firearm of a police official and shot him in the head.
“The man then shot two patients who were in his proximity. Both died on the scene.” She said.
She said SAPS officials on the scene subsequently disarmed the suspect and arrested him.
Potelwa said the names of two other people aged 42 and 48 who were killed are yet to be released.
Western Cape provincial commissioner Lt-Gen Thembisile Patekile has conveyed condolences to the family of the deceased policeman.
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