Musk is not alone. Bill Gates, Steve Wozniak, Steve Hawking and Noam Chomsky are also out with similar public statements.
Should we be afraid? Yes. Why? Humans deem themselves superior to all other less intelligent creatures and either consume or keep them around as pets.
Will such irony unfold? A species manufacturing it's master? Well, consider every weapon developed has been used. So no doubt super-intelligent machines will be allowed out of the box.
Likely the only way to keep up is to become The Borg, right?