Great-grandmother Angela Evans, 67, lay face down in the sand motionless with her friend and neighbour Belda Butauskiere, 49, for 10 minutes during the bloodbath while gunman Seifeddine Rezgui murdered already wounded holidaymakers in cold blood.
Mrs Evans, of Kings Lynn, Norfolk, told how he stood over her and reloaded to “finish her off” but was distracted by noises further up the beach.
The distraction saved her life.
Rezgui, 23, arrived on the beach in an inflatable boat at noon on Friday, dressed as a barefoot tourist in shorts and top.
He pulled a Kalashnikov from an umbrella and began his rampage of murder, deliberately targeting westerners.
In a strap around his chest he carried home-made grenades, padded with ball bearings, which he hurled at guests inside and outside hotels.
After 20 minutes he was shot dead by Tunisian security services.
Describing her ordeal, Mrs Evans said: “We were lounging on the sunbeds when we heard noises similar to firecrackers. I looked up and there was the gunman dressed in black. He was shooting indiscriminately at people.
“He then approached those who were dying and shot them execution-style. We tried to run but had fallen over in a panic. I whispered to Belda to play dead and we both just lay flat, face down in the sand, as though we were corpses.
“I could sense the gunman was close by. His feet were just inches from my head. Then I heard him change the magazine in his gun. At this point I began to say a prayer in my head. I thought we were next and he was going to finish us off. But at that moment we heard some commotion elsewhere and he seemed to be distracted by that and wandered off.
“We played dead for about five more minutes until we heard screaming coming from the hotel lobby and we knew that’s where he had headed.
“We then got up carefully and wandered to the hotel next door, the Bellevue. On the way we saw holidaymakers lying dead with bullet holes in them. When we got to the Bellevue a member of staff hid us in his office until everything calmed down.”
Mrs Evans, a grandmother-of-four and great-grandmother-of-one, flew out on Thursday and was supposed to be in Tunisia for a week.
However, last night she and Mrs Butauskiere were preparing to fly home.
She said: “I’m still in shock. This is the last thing you expect to happen on holiday. I’m just so thankful that myself and Belda are OK, but my heart goes out to those who lost their lives.”
Mrs Butauskiere, who lives next door to Mrs Evans in Kings Lynn, said: “When we first saw the gunman we mistook him for a police officer.