This movie was aired on TV about 14 years ago. I don’t know the original language of the movie.
An elderly man lived in an apartment building. He happened to have some irritating neighbors who either made too much noise or somehow irritated him. He decided to kill them and each time he made his decision, he made this weird gesture: he put two fingers on his lips — a gesutre which probably meants he was thinking, contemplating the way he’d kill them.
Then there is this detective who is after him and finally proves he’s the murderer, but eventually is killed by him as well.