Guesses about the end of Mankell's first Wallander novel

Many have encouraged me over many years to read Henning Mankell's Wallander detective novels - because I've lived in Sweden and written about Sweden - but I've been reluctant in that I rarely read crime fiction and I was disappointed to say the least in the last Swedish crime novel people said I just had to read - Dragon Tattoo - but anyway I felt as if I needed a break after a lot of reading of great short stories mostly from the early 20th century so picked up Mankell's first Wallander novel, Faceless Killers, and so far find it pretty good - not high literature by any means, but it has the crisp and skeleton narrative style of good crime fiction, sets up a very puzzling murder at the outset - breaking from convention a bit by beginning the novel from the viewpoint of the elderly couple who discover the murder victim, a friend and neighbor killed in the night in his farmhouse. By and large these novels live and die not only on their technical skill w/ plot but mostly on ability to evoke a setting and on the development of the protagonist's character. The southern Sweden setting (Skane) is exotic only to a degree; I've only passed through but by and large its flat farmland, pretty well populated, pretty homogeneous Swedish population although, as this novel hints, there are some tensions w/ recent immigrants from Eastern Europe. The setting doesn't seem to be a dominant characteristic here. Mankell's Wallander is a pretty interesting guy, and fairly typical of the genre: alone (recently divorced or separated), mid 40s, taciturn, smart, opinionated; they always have a peculiar tic or passion and in W's case it's a love of opera - although I'm not sure if that defines him in any particular way, and his taste w/in opera seems pretty standard - in the first few chapters he doesn't venture beyond Verdi classics. I have my guesses about the plot, which I'll share for the record: the non-whinnying horse has to be a big clue (echo of Hound of the Baskervilles), so I suspect whoever killed the farmer was known to the horse - and therefore guessing it must have been one of his children (or the one of the children of the neighbor who discovered the murder): Mankell went to the trouble of referencing the children who used to play together, and he has set up a sub-plot with Wallander's wayward daughter. Why a child would brutally murder a parent or neighbor, that's the mystery - maybe something to do w/ the influx of Rx as a new wave of immigrants enters the once isolate and placid country (immigration a big issue in the southern part of Sweden - something Knausgaard has written about as well).