Turkey backed its story with solid evidences, most of which were also confirmed by third parties. That's why we enjoy international support while Russia is busy taking its "revenge" from the Turkish students and businessman in the country.
There have been countless warnings at every level. In their previous violation, their ambassador was summoned and warned. The necessary warnings had been issued directly to their PM and President by both Turkey and NATO (
Syria conflict: Nato warns Russia on air strikes - BBC News). They were warned about the "extreme dangers" of their possible future violations. Unfortunately, Putin chosed to ignore it.
So if there is a murderer here, it is Putin.