Investigators in Santa Ana are still searching for answers, including finding out where she may have been killed.
Police have been trying to trace the final hours of Alicia Rosales' life to determine how the 20 year old end up dead in the back of her vehicle in Tijuana.
Authorities said Rosales' aunt, who lives in Chicago, called Santa Ana police claiming there might be a domestic violence dispute between Rosales and her 24-year-old boyfriend, Daniel Lozano.
"We get a call from the aunt who states that she received a cell phone call from her niece who was in Santa Ana, stating 'He's going to kill me,' then hung up," said Cpl. Anthony Bertagna of the Santa Ana Police Department. "The only thing we had was the cell phone number. We continued to call that. No response."
Rosales and Lozano, who had two young children together, had recently split.
Rosales' uncle in San Jose, Calif., also filed a missing persons report.
Police said they went to the couple's home in Santa Ana to find out they had moved out a few weeks earlier.
Lozano's parents stopped by the police station and told detectives they were worried because Lozano had dropped off the kids a week ago and they couldn't get a hold of him.
Mexican authorities on Tuesday made the tragic discovery on a downtown street in Tijuana.
"It was their truck," Bertagna said. "She's in the back of the truck. There's apparently some blunt force trauma to the victim."
Investigators allege Lozano admitted to Mexican authorities he was responsible for her death.
"He told authorities he went down there to commit a suicide pact," Bertagna said.
Police are now trying to sort out whether it was a suicide pact or if Rosales was kidnapped in Santa Ana and killed in Tijuana. They also want to know why and how she was murdered.
Bartagna said he hopes friends and co-workers will come forward to help them tie the case together.