When he was come down from the mountain, great multitudes followed him.
This is the quote from KJV Bible. I am doubted why to say "he was come down". I felt "he came down" is more proper grammatically.
Be + Verb in pp form is usually a passive voice which seems irrelevant in this context. However, I did hear a lot native English speakers say 'he was come down', 'are you agree with me?', etc. Is this usage correct?