apple id belongs to another person
i recently bought an ipad from somebody in the us through somebody but he forgot to erase the device and now i cant set it up coz its still link to his apple id , whenever is enter mine ir rejects , tried reseting and it does not go remove that person's id either , and to make matter worse i dont know the guy, how do i activate my device so i can enjoy it?
iPad, iOS 7.1