Federal marshals say Matthew Flores Semyonov remains wanted after his parents were found buried behind their Litchfield Park home.

LITCHFIELD PARK, Ariz. — An international search remains underway for 27-year-old Matthew Christopher Flores Semyonov, an Arizona man authorities accuse of killing his parents and concealing their bodies in the backyard of their Litchfield Park home before leaving the United States. The U.S. Marshals Service continues to list Flores Semyonov as a wanted fugitive in connection with the deaths of Hector Flores, 69, and Larissa Flores, 63.

The federal fugitive case grew out of a missing-person investigation that began in early August and quickly became a double-homicide inquiry. The U.S. Marshals Service says Flores Semyonov is wanted federally for unlawful flight to avoid prosecution and by Avondale police on allegations including first-degree murder, dangerous domestic violence and abandonment or concealment of a dead body. Those accusations remain allegations, and Flores Semyonov has not been brought before a court to answer them.

The U.S. Marshals Service took a leading role in the search after Avondale police formally requested federal assistance Aug. 7. Marshals said investigators had concluded Flores Semyonov had fled the United States, although authorities have not publicly identified the country where they believe he went or explained in detail how they determined he had crossed an international border. A federal warrant was obtained in U.S. District Court in Arizona, allowing federal agencies to coordinate a search that can involve law enforcement partners outside the country.

The case began Aug. 4, when a son of Hector and Larissa Flores asked police to conduct a welfare check at the family home. According to a police report described by local news organizations, the relative said he had not heard from his mother since July 29, even though they normally communicated frequently. Calls to Hector Flores, Larissa Flores and Matthew Flores Semyonov went unanswered. When the relative met officers at the residence, he allowed police to enter but remained outside because he was afraid of what they might find.

Officers did not find any of the three family members in the home. Police later said they encountered a significant amount of blood and signs that someone had tried to clean it. The discovery shifted the case from a routine welfare check toward an investigation into possible foul play. Authorities also attempted to locate the family members through their cellphones, according to reporting on the police report, but the devices were turned off and could not be located through the carrier.

The search then moved beyond the interior of the house. Investigators examining the property discovered two bodies buried in the backyard. Avondale police later identified the remains as Hector and Larissa Flores. Earlier reports said the bodies had been placed in separate shallow graves. The Maricopa County Office of the Medical Examiner initially listed the causes and manners of death as pending, and authorities have not publicly provided a complete account explaining when the couple died or precisely what happened inside the residence.

A police report released after the discovery also described concerns raised by relatives about Flores Semyonov before his parents disappeared. A family member told investigators that Flores Semyonov had learned his father was having an affair and had become upset that his mother had chosen to remain with him. The relative also recalled Flores Semyonov making vague threatening remarks, including the statement, “you’ll get what’s coming to you.” Investigators have cited those family accounts, but authorities have not publicly established the marital dispute as a proven motive for the killings.

The same report contained descriptions of changes relatives said they had noticed in Flores Semyonov after college. Family members said he moved back into his parents’ home, became less social and changed parts of his lifestyle. The report also referred to a mental health diagnosis, but the diagnosis was redacted in material released publicly. One family account described Flores Semyonov watering plants during the night and saying the plants had told him they were thirsty. Those statements are part of witness accounts collected by police and do not, by themselves, establish why the deaths occurred. Authorities have not announced that any medical condition caused or contributed to the alleged crimes.

Behind the criminal investigation are two victims whose careers extended well beyond their Litchfield Park home. Hector Flores was an associate professor in the Department of Management and Human Resources at California State Polytechnic University, Pomona. The university said he joined the faculty in 2015, taught strategic management and other business courses, conducted research and took part in faculty governance. Before entering academia, he had worked in private industry. The university remembered him for his work with students, colleagues and faculty organizations.

Larissa Flores worked in health care and was a psychiatric nurse practitioner associated with Circle the City, a Phoenix-area organization that provides medical services to people experiencing homelessness. The organization described her as a valued colleague who cared deeply about patients and treated them with compassion and dignity. Those professional tributes emerged as police publicly confirmed that the bodies recovered from the backyard belonged to Hector and Larissa, shifting attention from the initially unidentified remains to the lives of the couple at the center of the case.

The Flores Semyonov family, through a representative, said relatives were devastated by the deaths and cooperating with law enforcement. The family asked for privacy while the investigation continued and thanked friends, neighbors and community members who had expressed concern. Investigators have not publicly described all evidence they believe connects Flores Semyonov to the killings, and portions of the underlying police report have remained redacted. No publicly reported court proceeding has yet provided an opportunity for the evidence against him to be challenged by a defense lawyer.

Federal authorities have continued to treat finding Flores Semyonov as the immediate priority. The Marshals Service describes him as 6 feet tall and about 177 pounds, with blue eyes, and says he should be considered dangerous. The agency has coordinated with domestic and international law enforcement partners while Avondale police remain responsible for the underlying homicide investigation. Officials have not announced a suspected destination, an arrest or his return to Arizona.

As of Sept. 22, Flores Semyonov remained listed on the U.S. Marshals Service website as wanted for first-degree murder and unlawful flight to avoid prosecution. His whereabouts remain publicly unknown, leaving the criminal case without a defendant in custody and several central questions — including the full circumstances and timing of Hector and Larissa Flores’ deaths — unresolved as the international search continues.

Author note: Last updated September 22, 2026.