For "atheist explanation", you mean "unbiased by religion and only based on fact", right? I'm just saying because the way you asked sounded akin to asking the opinion of a sect or anything that's organized. Atheists are individuals.

My own personal hypothesis is that the story he's telling us (remember, this is the account of one man, no other people in that video told us they saw the angels there, this is all based on his testimony) is how his brain tried to cope with what was happening. It was obviously a traumatic experience, psychologically and most importantly physically. The man was being crushed beneath a truck, and was losing conscience due to the intense pain.

Let's bear in mind that he's not telling us this story 5 minutes, 10 minutes, an hour after the fact. Months have passed. He's had time to "reconstruct" the event in his mind, and to "interpret" things the way a man of faith would.

In the few minutes spent trying to write this answer I actually found this rather interesting analysis, I would insist that you read it. If the sardonic remarks about God in it offend you, you can ignore them, I feel the thing in itself is worthy of attention and thought.

http://www.freethunk.net/freethunk-news-bites/bruce-van-natta-grows-intestines-say-what-2949

Final thoughts: medical science saved Mr Van Natta. Just because he claims it's a miracle, and God helped him, doesn't mean it is. I feel what he claims is very disrespectful to all the doctors and surgeons responsible for him being alive today. Not a word of gratitude is spent towards them in the video and I feel that's a real shame.