"She had been shopping, and it is possible she was followed home," he said.
"She opened the garage door with her remote and drove in, and was followed in by one thug. His accomplices threatened the guard and the maid with a gun - the staff had been chatting outside the house.
"Lois lost her bag, her phone and some jewelery. She is a very calm person, she reassured the robber, told him to keep calm.
"She won't let this get her down, she is strong. This is how we live in South Africa, there is a full time guard in a guard house just outside the garage and the thugs were brazen.
"It doesn't matter where you stay, what security you have, crime is everywhere and any time of day."
According to a local police source, the Pistorius's housekeeper and guard were ordered at gunpoint to lie face down on the floor, so they could not put up a struggle.
Mrs Pistorius "cooperated fully" with her attacker after he brandished a heavy hammer in her face and ordered her to take off her rings.
"It was obviously a terrifying experience for her, she wasn't expecting to be confronted by an intruder on her own property - we regard inside the garage as a house robbery,' said the source.
"She stayed calm and cooperated fully with the robber and immediately removed her rings and handed them over, and apparently was reassuring to him, letting him know that she posed no threat and would do as he wanted.
"He also pointed to her bag which was sitting on the front seat and she handed that over.
"The robber did not raise his voice according to the victim, but he was armed and brandished his weapon very obviously, so the threat was clear to her - cooperate or face the consequences.
"Later Mrs Pistorius' phone was found discarded, which is common as the expensive phones have trackers and robbers know they run a risk of being caught if they hang on to them.
"Mrs Pistorius was offered trauma counselling but said she did not need it. Her guard, who was threatened with being shot, has requested some counselling, however."
Pistorius moved into a cottage on his relatives' large property following the Valentine's Day murder of Reeva Steenkamp, 29, in 2013.
He returned there under house arrest after serving a year for her manslaughter, until he was re-sentenced to six years for murder last year, following an appeal.
Today, another of the runner's relatives told the MailOnline, "This situation is exactly what you have to consider when you look at Oscar's behaviour on the night Reeva was shot.
"He had every reason to believe that someone was in his house and that he and Reeva were in danger.
"Crime in our country is out of control, you can't seem to do anything to protect yourself, and there is no one else looking after your security.
"You are responsible for yourself and loved ones and that is it. it's just lawless."