SAN ANTONIO — Police say they've arrested a suspect in the murder of a 19-year-old girl found after a desperate call for help that came too late.

San Antonio Police found 19-year-old Erin Castro dumped along Camp Bullis Road early Sunday morning. By that evening, they had arrested her boyfriend, 20-year old Joshua Garcia.

The call for help came around 1 AM from Castro's mother. The dispatcher said the mother was on the phone with her daughter, but the young woman had stopped responding.

Castro's mother told police that her daughter had been stabbed by Garcia, who dated her daughter on-and-off for years, and was unsure of their location. Castro's phone was traced to an area on Camp Bullis Road just east of I-10, and officers found the victim in the roadway with catastrophic injuries.

One officer said the woman had two significant wounds and asked that EMS respond quickly. The response was not enough to save the woman.

Police contacted Garcia's mother, who told investigators that he had admitted to her that he'd run over Castro. His brother told police that Garcia had called him for help after the couple broke out into a fight. The brother said he witnessed Garcia run over Castro several times.

Garcia is facing one charge for murder and remains behind bars.

Court documents reveal that Garcia is currently on probation for a felony aggravated assault with a deadly weapon offense. Garcia also has previous charges for burglary theft, and evading arrest.