The motive for the murder was, Kellerman wanted Butler out of his house. Now I've never heard anything about gay activity between them but like @KINGSAPIO said, they were friends. Kellerman was helping Butler out by letting him stay with him, as time went on Butler became erratic, and menacing, and Kellerman wanted him to leave.Butler and Kellerman's brother were having a gay relationship...don't remember what the exact motive was either though