Nelson's father, Harldur Nelson, explained to MMAFighting.com what happened via e-mail:
"A pickup [car] he was in (they were four in the car and Gunnar was in the passenger front seat) went off the icy road and rolled down a hill three-to-four times. It ended up on its wheels in Þjórsá, but that is Iceland’s longest river. It’s a very cold glacier river with very hard current. If the car had gone few feet further into the river it would have hit deep waters and the current would have taken it. So they were very lucky. Also, if they had gone of roads few meters before or later it would have been much worse and they would also have gone in the river.
"All of them got away with scratches basically (they were all wearing seat belts, of course), even though Gunnar had to have around 10-11 stitches in his arm. But he’s fine and will be ready to start training again in a short while."
The other three passengers in the car walked away with similar minor injuries. For a picture of their car after the accident, click here.
Nelson's father added that his son is hoping to return to the UFC in the first quarter of 2014. The 11-0-1 Icelandic fighter is currently 2-0 inside the Octagon.