YOU SAID:

I was coming back from work when i saw him coming back home

INTO JAPANESE

彼が家に帰ってくるのを見たとき、私は仕事から帰ってきた

BACK INTO ENGLISH

I came home from work when I saw him coming home

INTO JAPANESE

彼が帰ってくるのを見たとき、私は仕事から帰ってきました

BACK INTO ENGLISH

I came home from work when I saw him coming home