(NBC News) - Carson Urness, a 3-year-old North Dakota boy, is best friends with his family’s dog, Cooper.

The Urness family adopted the golden retriever-German shepherd mix as a puppy after finding him abandoned on the side of the road.

Since then, he and Carson have been regular playmates and often frolic in the yard together. But Monday night, they went a little too far. Carson’s mother called 911 after she couldn’t find him in the yard.

Even more troubling, it was getting dark, raining and the family’s house backs up to more than 2,000 acres of North Dakota farmland. More than 200 volunteers searched for Carson that night.

Highway patrol dispatched aircraft searches for the boy -- still no sign.

Then, at 2 a.m., a firefighter trekked over a hill about a mile away from the family’s home and caught something with his flashlight: Carson lying face down on the ground asleep with Cooper the dog on top of him keeping him warm.

Aside from some torn jeans, a ripped jacket and a little mud, the little boy is fine.