A man was arrested in northern Mexico's Nuevo Leon state after he wrote a Facebook post confessing that he killed his fiancee's mother, according to a report from IANS Live.

Roberto Alejandro Santos, a 32-year-old schizophrenic, is being detained under suspicion of killing 61-year-old Lucilia Reyes, said David Perales, Nuevo Leon's prosecutor's office deputy spokesman. Santos was arrested on Sunday.

"I did it," Santos wrote on his Facebook page. "I don't know how they can let me live another day."

Police found Reyes' body on Saturday afternoon at her residence in the city of San Nicolas, which is a suburb of Monterrey less than 150 miles from the U.S. border. Police believe that she was killed earlier that morning.

Even before the incriminating Facebook post, Santos was already a person of interest in relation to the murder. Santos' fiancee had filed a police report claiming domestic violence.

Despite what seems like a clear confession, the Facebook post alone won't be enough to charge him with the murder and the case against him will hinge on what he tells police.

Santos now is being held on a preventive arrest order, which could detain him for up to 30 days. After the order expires, a judge will decide whether to charge him with the crime.

According to the National Institute of Mental Health (NIMH), "schizophrenia is a chronic, severe and disabling brain disorder that has affected people throughout history."

There has been no report on any symptoms that Santos might have displayed, but schizophrenics are sometimes known to hear voices that others do not hear, and, according to NIMH, believe "that other people are reading their minds, controlling their thoughts or plotting to harm."

These beliefs can often terrify those with the illness and cause them to be withdrawn or very agitated, sometimes leading to violent behavior.