A security guard is behind bars and is facing murder charges after he allegedly shot dead an 18-year-old boy in Atholl, in northern Johannesburg, on Sunday night.

The teen was walking home with a friend when security guards approached him and shot him.

The police's Moses Maphakela said the guard may have thought he was a robber.

The teen had been living with his mother at her employer's house in Atholl.

The mother?s employer Della Essakow is demanding answers: "The guard pulled out a gun and shot him. The poor child of 18 is laying dead."

The guard will appear in court soon.