A Scottburgh police officer shot and killed a murder suspect who overpowered a colleague at the local police station on Friday, KwaZulu-Natal police said.

Sixoliseni Nkonya (26) was being interviewed by a detective investigating last Tuesday's murder and attempted murder of an elderly couple in Marine Terrace, Captain Vincent Pandarum said in a statement.

Nkonya asked to use the toilet. When the officer unlocked his handcuffs he turned on him and a struggle ensued.

The officer called for help and a colleague came running. He kicked open the door of the cubicle and apparently shot Nkonya, who was pointing the officer's gun at him, in the chest.

He was declared dead when paramedics arrived.

Forensic evidence was used to connect Nkonya to the Marine Terrace attack. He had stabbed a 70-year-old man 25 times in the body and legs. He was found dead about 500 metres from his flat, having left a trail of blood, indicating that he may have been looking for help.

His wife was taken to hospital with 10 stab wounds. She was in a critical condition, but recovering.

"The motive for the attack has not been established as yet and does not appear to be robbery, as nothing was found to have been stolen from the victims or from their flat. A kitchen knife was found at the scene and will be subjected to forensic tests."

Police records showed Nkonya had earlier been arrested for the robbery of a woman in Durban North, and was released on warning.

"He was due to appear in the Durban court yesterday [Thursday]. However, when the Scottburgh SAPS detectives went to the court to arrest him, he failed to pitch up for his case."

"He was traced to the Durban Central police station cells where he had been detained for allegedly breaking into a house the previous night."

Nkonya was transferred to the Scottburgh police station, where the shooting took place on Friday around 1pm.

An inquest docket was opened and the Independent Complaints Directorate informed.