Fresno County investigators believe Gabriel Rosiles, a known gang member, killed his girlfriend at a mobile home on Cherry, between North and Central.
The crime scene is the same place where a double murder occurred just a month ago.
Investigators say 23-year-old Rosiles killed his 30-year-old girlfriend but they are not revealing how she died but she was reportedly beaten to death.
Rosiles was on parole for stealing cars.
The victim's name has not been released.
Three men who also lived in the trailer were arrested for killing two men outside the home a month ago.
The Fresno County Sheriff's Department does not believe the two crimes are related.