If it was an assassination, by who? By the state? That makes little sense to me as why would the Turkish government want to foment further unrest at such a tense and conflicted time? To justify further security crackdown? Don't think so, they don't need further excuse.
I'd be surprised if it was not Daesh people or sympathizers, as who more would love to see more Turkey unrest.
Or by one of the most ultra-nationalist extremists in opposition to Erdogan.