How exactly did lightning kill 323 reindeer in Norway?

Lightning during a recent thunderstorm in Norway killed a herd of 323 reindeer — 70 of them calves — making it one of the deadliest strikes ever. Hunters in a remote area discovered the bodies last Friday, according to the Norwegian News Agency.

We usually hear about lightning striking people, but it does kill animals , too. Two scientists at an Australian research institute have found that everything from seal pups to wild turkeys to elephants and giraffes can be killed by lightning.

Was this a freak accident, or is it common? And how does this happen? I spoke to John Jensenius, a lightning safety expert from the National Oceanic and Atmospheric Administration, to learn about the science behind these deadly herd strikes. (This interview...