An old, ornery bounty hunter returns home for his estranged son’s funeral and finds he must stop the men who killed him before they kill his grandson.

In a lawless Western town, a retired bounty hunter must kill the men who just killed his only son before they kill his only grandson.

I presume the setting to be in the Old West. ?I added "only" to raise the emotional and existential stakes: the threat of the extinction of the protagonist's lineage and surname.

Wait, who's killing or gonna kill or killed whom? And why?