Lightning travels down the side of the tree-trunk and then encounters the person standing next to the trunk. This person is made up of slightly salty water which is a better conductor. Instead of just the tree-trunk, lightning strike finds that a combination of the two is much better. So, a subsidiary strike connects to the top of the person and travels to the ground that way, possibly killing both the tree and the person.
Why shouldn’t you stand under a tree that has been struck by lightning?
