That is a gruesome passage, but an awful lot more could have been described in detail. The reader's imagination will create all that you have left out and this is one of the advantages the written story has over the visual. The reader will see what he wants to see. Implication is always preferable, subtlety has a greater impact than a gory passage. And, if you like, you can describe the mutilations in a documented manner in a later conversation between pathologist and police officer.
Violence is different from horror.
The former sickens, the latter frightens. The icy touch on the back of the neck on a dark night is terrifying, the bloodied mutilated body is revolting. Graphic carnage is best avoided or not described in full, mutilation must have a reason that fits the story. Those horror books of the early 1970s are a couple of decades out of fashion. In defence of violence in books, I do not accept the media's claims that violent books create violent people.