[@MissCapnCrunch] I would advise you to keep the one that commits the crime hidden - so that all characters may be a suspect. Or at least, those close to him..

Grey insulted him,
Lucan is close to him, lacks a motive but it'd be easy to place blame on him,
It's likely that Amara might be implicated due to her hatred for the family (even if the hatred is invisible, the act of her family being murdered would give her a motive and that's really all that is needed)
I'm not sure if the Hylands' ambitions are public, or not, but if they are public or they are suspected of having ambitions, then that'd be a motive too.. 

Plenty fingers to point.