YOU SAID:

there was a man in the alley, who was looking at me.

INTO JAPANESE

路地に男がいて私を見ていた

BACK INTO ENGLISH

There was a man in the alley looking at me.

INTO JAPANESE

路地に男が私を見ていた。

BACK INTO ENGLISH

A man was looking at me in the alley.

INTO JAPANESE

路地で男が私を見ていた。

BACK INTO ENGLISH

A man was looking at me in the alley.