Cape Town - A Mitchell's Plain police detective is believed to have shot and killed his girlfriend and her mother before turning the gun on himself at the girlfriend's Lentegeur home.

It is believed that Detective Sergeant Granville Brooks, 41, attended detective training in Oudtshoorn and on his return home on Wednesday night an argument broke out between his partner and himself.

On Thursday morning shortly after 9 am, four or five shots were heard coming from the property. 

Soon afterwards police and EMS workers arrived on the scene.

Details about the incident are still sketchy, but shortly after 11am police snipers reportedly used smoke grenades to enter the house and found the three bodies inside.

The father of Brooks' girlfriend who was reportedly also in the house, is believed to be the only survivor.

It is believed that all the alleged shootings took place in the bedrooms in the Lentegeur home.

Brooks is divorced and the couple have been dating for a few years.

The police have yet to comment on the incident.

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* This is a developing story and will be updated as more details become available.