This could easily be the Dutch equivalent of "Snakes on a Plane". Not because the stories are similar, obviously, but because both films have a pleasant-sounding title that describes the entire plot and simultaneously attracts curious viewers! The title literally translates as "Herman Kills People", and that's exactly what Herman does.
The first half is a deliciously over-the-top and effectively satirical black comedy. Socially relevant, too, because Herman isn't a natural born killer, but a troubled senior citizen struggling with alcoholism and a lack of professional care. He learns that he would receive better guidance in a prison than in his expensive retirement home. So, Herman thinks of a plan that'll help both himself and a poor neighborhood girl, namely by killing her abusive husband. But nobody takes an old man who smells like booze seriously, not even when he confesses at the scene of the crime.
It's twistedly funny and very, very recognizable. Everyone who lives in The Netherlands (or in Belgium, for that matter) will have somehow experienced the frustrating bureaucracy, here masterfully illustrated via the fake-compassionate social worker, and the sheer hypocrisy that homes in all of us; - like how people in a retirement home are only interested in a room-upgrade when a fellow resident passes away.
Unfortunately, and quite unbelievably, the tone of the film makes a complete U-turn slightly over halfway. "Herman Vermoordt Mensen" becomes a sentimental melodrama with a lot of dull dialogues instead of sadist murders, melancholy instead of satire, and flashbacks instead of black comedy. Herman even miraculously cures his alcohol addiction, and walks more straight with a broken hip than he does with rollator.