YOU SAID:
I think it was someone entirely new
INTO JAPANESE
まったく新しい人だと思います
BACK INTO ENGLISH
I think that he is a completely new person
INTO JAPANESE
彼は全く新しい人だと思います
BACK INTO ENGLISH
I think he is a completely new person
INTO JAPANESE
私は彼が全く新しい人だと思います
BACK INTO ENGLISH
I think he is a completely new person
That didn't even make that much sense in English.