Constable Tokolo Puntsa Chala, 33, was sentenced on Tuesday to a total of 18 years in prison, Independent Police Investigative Directorate spokesman Moses Dlamini said on Wednesday.
Twelve years were for the murder and three years each on the other two counts.
The court suspended six years from his murder charge and wholly suspended both three-year sentences for the other two charges.
In November 2009, Chala shot and killed his 22-year-old girlfriend, Dlamini said.
He later went to his other girlfriend’s home, broke into her house and shot the girl’s mother.
“The mother of his girlfriend sustained a gunshot wound to the leg while attempting to wrestle the gun away from the accused.”