Asian Movie (Similiar to Orphan)

Maybe here I find help.

Years ago I saw a movie, maybe a remake or the original of thiss movie.
But I don't know the name anymore.

A police officer and his girlfriend take a orphan kid (little boy) home
and he lives with them.
always tries to get closer to the woman and trying to push out the police boyfriend.

At the same time there are some murders happen, all done by a hobo.
But the little kid ordered him to do the murders.
And in the end the police guy finds out and tries to warn everybody,
but nobody listens and he stands with the "kid" on a sea platform and gets killed.
The "kid" turns out to be an old man doing this scheme for years.

Anybody knows the name?
Problably a korean movie...