Guttenfelder, who is the chief Asia photographer for the Associated Press news agency and a frequent National Geographic contributor, read about it on Twitter while traveling in a car from the capital city of Pyongyang to the far northeast corner of the country, near the Russian border.

"There's 3G service in North Korea now, weirdly ... [and] I started to read about the scale of the destruction," Guttenfelder said. "I saw a picture someone had tweeted of the typhoon taken from space, which was really amazing."

But it wasn't until he saw another tweet, about the death toll from the typhoon, estimated to be in the thousands, that Guttenfelder knew he needed to see the devastation firsthand. "My job was to cover