A man walks into a transportation station and two officers in neon jackets stand guard.
The guards are watching a suspicious man
Standing guard deosn't imply being guards and nothing says that the two officers are watching something. Walking into a transportation station doesn't imply being a suspicious man.
The man who walks into the station may be not a suspicious man the guards are looking at.
A man walks into a transportation station and two officers stand guard doesn't imply the guards are watching a suspicious man.