Mostly the only thing that i could dig up on shapeshifters is that they are very, very hard to kill.
I will give you some insight on how you should treat these creatures.
Many people say that shapeshifters can turn into any number of animals or they can completely resemble the physical features of any person that they see. That is why not many people know much about them.
Description: Shapeshifters were once human, ussually the ugly kid, the one that no one liked, parents were killed, and ussually had foster parents. The folklores say that shapeshifters were very mad, and also hated everyone and everything. They will have scars, and also disfigured.
Ways to Kill: You can kill them the same way you can kill anyone. Gunshot, knife, mostly anything you can think of to kill a human.