Guilty plea from Mario Chacon to tampering with evidence in the 2023 death of his former girlfriend, Madeline Pantoja.

MIDLAND, Texas — A 27-year-old Midland man has been sentenced to 35 years in prison after pleading guilty in the 2023 killing of his former girlfriend, 20-year-old Madeline Pantoja, a case that began as a missing person search and ended with a murder charge and a second conviction for tampering with evidence.

Mario Juan Chacon entered guilty pleas Feb. 20 in the 142nd District Court to murder and tampering with evidence. Judge David G. Rogers sentenced him to 35 years on the murder count and 20 years on the tampering count, with the terms to run at the same time. The plea brought a formal end to one part of a case that drew intense local attention in Midland in May 2023, when Pantoja vanished from her apartment and police, state investigators and federal agents joined a round-the-clock search.

Pantoja was last known to be alive the night of May 10, 2023. Friends later told investigators they had spoken with her that day, and one of her last messages involved plans to go swimming at her apartment complex the next day. When calls and messages went unanswered, friends went to her apartment at Palladium Museum Place on West Francis Avenue, but no one answered the door. On May 11, officers were sent to the apartment for a welfare check after a request from Pantoja’s brother. Police still could not make contact. On May 12, after another caller reported hearing a woman’s voice from inside, officers entered the apartment. What they found deepened concern. Police said there was a mop and a bucket of dirty water near the front door, the floor was unusually sticky, and Pantoja’s coffee table was gone. Officers also found damage to interior doors, hair attached to one damaged bedroom door, a missing comforter and a large red stain on a bedsheet. Friends told investigators Pantoja would not have left her dog without food or water.

Chacon spoke to police more than once in the early days of the investigation, and detectives said his account changed. In an initial interview, he said he had last seen Pantoja on May 9 and last spoke with her by phone on May 10 while he was at home. In a second interview, he added that he had met up with a cousin on the night Pantoja disappeared and had driven that cousin back to the same apartment complex where Pantoja lived. Chacon said he went home before 11 p.m., but investigators later said surveillance footage placed his pickup near the complex much later. According to court records, traffic cameras, private video and cellphone location data were used to track his movements from 12:26 a.m. to 3:37 a.m. Detectives said one of the final images showed him near a rural county road southeast of Midland at 3:22 a.m. During a third interview on May 18, detectives confronted him about what they described as lies in his timeline. He responded, “OK,” and asked to leave, and investigators let him go at that point.

Two days later, the case turned sharply. On May 20, searchers used phone records mapped by Texas Rangers to focus on a rural stretch of Midland County near County Road 190. Human remains were found that day and identified as Pantoja’s, first through jewelry and later through forensic work. Police announced Chacon’s arrest at about 3:30 p.m. on the same day and charged him with murder. Midland police said the remains were located in an area east of County Road 190 and County Road 1160. Court records also described a search zone around County Road 190 and County Road 1138. Authorities did not publicly spell out every detail of how the body had been concealed, though later reporting cited a source close to the investigation who said the remains were found inside Pantoja’s missing coffee table. Police statements available at the time focused instead on the discovery of remains and the continuing investigation. That distinction remained important because the coffee table detail became one of the most repeated facts in later accounts of the case.

The autopsy, performed in Dallas County, concluded that Pantoja died from a combination of strangulation and suffocation. Investigators said the attack also included a beating with Chacon’s hands and at least one object. Those findings gave prosecutors a clear medical basis for the murder case and helped explain the damage officers said they saw inside the apartment. By then, the case had already shaken Midland, where public rallies called for answers while police defended the pace and scope of their work. At a May 19 news conference, then Police Chief Seth Herman said investigators had searched about 60 square miles of remote property, executed more than a dozen search warrants, interviewed about 25 people and followed up on about 20 tips. He said the search effort involved the Midland County Sheriff’s Office, Texas Rangers, the FBI and Homeland Security Investigations. Mayor Lori Blong said city leaders were in touch with Pantoja’s family and supported the department’s efforts.

The criminal case then moved through the court system in stages. Chacon was formally indicted on the murder charge July 19, 2023. A separate indictment charging tampering with evidence followed on Nov. 19, 2025. He remained in the Midland County Jail on $3 million bond while the case was pending. Instead of going to trial, he pleaded guilty to both counts in February 2026. Rogers imposed concurrent sentences, meaning the 20-year tampering term does not add time beyond the 35-year murder sentence. Under the terms described by prosecutors and later reports, Chacon will receive credit for time already spent in jail awaiting resolution of the case, and he becomes eligible for parole after serving at least half of the sentence. Eligibility does not guarantee release, but it sets the earliest point at which the parole board may review his case.

The case left behind a record of fear, anger and grief that stretched well beyond the courtroom. In the first days after Pantoja vanished, friends and relatives kept returning to the apartment complex, checking on her dog, retracing her last known movements and pressing authorities for updates. Police said they understood the urgency but warned that independent efforts could interfere with an active investigation. That tension reflected the emotional strain already building around the search. By the time Chacon entered his plea, the broad outline of the case was no longer in dispute. Prosecutors had a timeline built from digital evidence, physical signs from the apartment, recovery of Pantoja’s remains and autopsy findings describing a violent death. What remained less clear in public records were the final minutes inside the apartment and whether prosecutors would have presented additional evidence at trial had the case gone that far. The guilty plea closed off that public airing, but it secured a conviction, a long prison term and a measure of finality for a case that Midland residents had followed for nearly three years.

The case now stands in its post-sentencing phase, with Chacon expected to move from county jail into the state prison system. Barring later appeals or post-conviction motions, the next milestone is his formal transfer and intake into state custody.

Author note: Last updated March 22, 2026.