You get a few assorted clues among the useless bits of chatter that the hobos give you. One of them claims to have heard "human voices" and "lots of yelling". Others implicate the local monsters; one of these claims to have seen some gnolls leaving the area after the murder, while another claims that murlocs had been "casing the joint for days, maybe months" before killing the Furlbrows, only to leave when Laine and the others arrived. Laine is not convinced. "Horse poopy, pal," he says. "I've seen what gnolls and murlocs do to people that they kill and this isn't it. Too pretty. But, seeing as how we have no other leads, we may as well chase down the information you got. This is murder, plain and simple, and we're gonna get down to the bottom of it. Try looking through the murloc and gnoll camps around. Maybe you'll get lucky, rookie."
Follow Laine's advice. See what you can find around here on your own. It's clear to everyone here that the gnoll and murloc clues are worthless. Look into the possibility of the "human voices".