Mark Castellano, 37, confessed Sunday to killing Michelle Warner, his ex-girlfriend and the mother of his 3-year-old son, said Houston Police Department spokeswoman Jodi Silva.
The Midland County Sheriff's Office received a call at about 2:30 p.m. from Houston police, who gave deputies a general idea of where a body could be located in the county, said Sheriff Gary Painter.
The Sheriff's Office's mounted patrol unit searched in conjunction with a Department of Public Safety helicopter and team of FBI investigators, and they discovered what Painter called a "partial grave" that contained the remains of a female.
The remains, which were found around 6:25 p.m. just south of the intersection of South County Road 150 and West County Road 1200, were removed from their burial site and will be sent to Harris County Medical Examiner's Office for a full autopsy, Painter said.
It appears Castellano had left his son with relatives while he disposed of the body, Silva said.
Castellano had told police last week that he was in Odessa with their son and agreed to give a statement.
Castellano said he killed Warner after they got into a heated argument at their home in Sharpstown, Silva said. Silva said Houston police were preparing murder charges against Castellano and the investigation is ongoing.