One possible motive could be jealousy. If the innocent person had something that others desired, like a relationship, a job opportunity, or property, it might lead to envy and ultimately murder.
I'm not sure which specific 'a murder of innocence real story' you are referring to. There could be many real - life cases that might fit this description. It could be about an innocent person being wrongly accused and murdered, or an act of violence against someone who was truly blameless.
It's still a mystery. Maybe it was someone with a hidden motive or a person who appeared innocent on the surface but had a dark side. The investigation could have missed some crucial clues.
It's hard to say for sure. The case might be complex and the true identity of the killer could be hidden behind multiple layers of clues and misdirection.