The film is from Belgium, and was released in 1992. It came out shortly after Reservoir Dogs and its
profile at the time was probably raised by the similarity in name to Tarantino's first film.
The serial killer does not do it for money (as far as I can recall), but just for the hell of it.
The film is a mockumentary, supposedly filmed by a group of film students (cf The Blair Witch Project) who met the killer by chance.
The killer is a funny, affable conversationalist, and he does a great interview: he tells jokes, he explains the small details about ballasting corpses, before throwing them in a flooded quarry. He introduces the crew to a drinking game -- Dead Baby Boys.
How we laugh at his japes, at the comedic ways he kills. When we (and the crew) later witness, and vicariously take part in, the horrific rape of a woman, witnessed by her family, before murdering them all, we the audience feel incredibly guilty about our laughter earlier on.
A great film.