Tell me I'm stupid but.......
I couldn't find any reference to this representing an actual novel or event so I took it to be open to any answer we could come up with.
I also could not see anything relevant under the anagram below the victim.
However, alongside the victim in the grid is a vertical entry that could represent two pieces of one of the weapon answers. It goes up to the only suspect who is followed by an S, which could be written as 's, ie. their house.
I therefore highlighted the entry alongside the victim and the suspect on the top row.