Quick clarification question about Warbreaker...

When Vasher breaks into Mercystar's temple, he makes an effort to knock out but not to kill anyone as he enters the palace grounds and later the underground tunnels. When Lightsong investigates at a later chapter, he says that a priest saw a second man wearing black following the first intruder, and that this second man killed some servants following the first burglar. Lightsong also notes that he can tell the priest is lying but can't confirm about what. What exactly is going on? Was there a second person wearing black tailing Vasher (Denth? Someone else?) or was that a lie told by the priest, and in that case, why was he lying and who actually killed the servants?

Thanks y'all!