You said:

Knew he was a killer first time that I saw him. Wonder how many girls he had loved and left haunted

into Japanese

私が彼を見たとき、彼が殺人者であることを初めて知った。彼が何人の女の子を愛し、幽霊を残したのだろうか

Back into English

When I saw him, I knew he was a murderer. I wonder how many girls he loved and left ghosts