The 34-year-old from the Dominican Republic learnt that his grandmother had passed away just hours before the opening round of his event at the Games in Beijing four years ago.
Having regained the title that he originally won in Athens in 2004, the veteran revealed that he had been running with a photograph of his grandmother tucked into his vest.
"I just wanted to make her proud so I've got her name on my spikes," he told reporters. "The day she died in Beijing it broke my heart.
"That's why I ran with the picture close to my heart."
Reports have claimed that Sanchez will announce his retirement from the sport over the coming days.