This didn't happen in the US, but it's a perfectly grisly example of a gender-based murder:
A 46 year old man faces a life sentence for the murder of a woman who broke up with him after coming out as a lesbian.
...
At his trial the court was told that Queen was likely still alive as Seaton began sawing off her head in a frenzied fit. Her blood soaked body was discovered wrapped in a sheet on a quiet North London street last November.
On the witness stand pathologist Dr Vesna Djurovic testified that Queen had suffered dozens of injuries before she died.