5 chilling details from the Thomas Perez Sr. case on Dateline

In August 2018, Thomas Perez Sr., from Fontana, California, stepped out for a routine two-minute walk to check the mailbox with his dog, Margosha. He never returned home, leaving his son, Thomas Perez Jr., in growing worry.

What began as a simple missing person report quickly spiralled into a harrowing ordeal of suspicion, intense police questioning, and a shocking false confession.

As covered in the Dateline NBC episode The Ruse, which first aired on December 5, 2025.

The case highlighted the raw vulnerabilities in police interrogations and the devastating impacts of doubt on a family. Perez Jr., who had already shown issues with mental health, suffered through hours of pressure, leading him to believe he had harmed his own father, a man who was alive and well.

The full episode is available now on Peacock, NBCUniversal's streaming service, and can be seen again on NBC. This is one of those cases that shows the real human side of what occurs behind law enforcement doors.

Dateline: 5 chilling facts about the Thomas Perez Sr. case

1) The sudden vanishing on a familiar path

On August 8, 2018, Thomas Perez Sr. left his Fontana home around 2 p.m. for a quick walk to the corner mailbox, accompanied by the family dog, Margosha. The neighborhood was quiet, and the route was one he knew well.

When Margosha returned alone about 30 minutes later, Perez Sr. was nowhere to be seen. His son, Thomas Perez Jr., who lived with him, waited through the afternoon and night but saw no sign of his father. 

The next morning, Perez Jr. called the Fontana Police Department to ask if anyone matching his father's description had been reported wandering.

Community officers arrived at the home and noticed items piled up inside, which raised initial concerns. A search of the property turned up ThomasPerez Sr.'s wallet and phone, but no immediate clues. 

The absence stretched into a full day, turning a minor worry into a full-scale missing person investigation.

This ordinary errand's unexplained end set the stage for deeper family strain and police involvement, as per People.

2) The 17-hour interrogation marathon

Police soon zeroed in on Perez Jr. as one of their main suspects, taking him into the station for interrogation on the night of August 8.

What was supposed to be a routine questioning turned into a marathon of 17 hours until the wee hours of August 9.

Detectives Robert Miller, David Janusz, and Kyle Guthrie kept Perez Jr. confined in a tiny room with little rest, despite his pleas for sleep after staying up the previous night searching.

They gave him food and breaks sporadically, including a drive around town to view empty lots, but the questions never let up.

Perez Jr., who had controlled anxiety and depression with medication, wasn't taking his doses during this period, which only added to his exhaustion.

The environment would later be characterized as one of relentless pressure, accusations, and disregard for requests for medical attention.

The length of this session, along with sleep deprivation, had left Perez Jr. physically spent and mentally groggy. At one point, he remembered his vision began to blur, and he was exhausted.

This extensive isolation underlined an endurance test that lay at the core of this investigation, according to the LA Times.

3) Deceptions involving evidence and the family pet

Throughout the interrogation, detectives used several false claims to build pressure on Perez Jr.

They told him that a cadaver dog had detected human remains in the family home and that bloodstains, later unconfirmed, covered the floors and even Margosha's paws.

Officers suggested the dog was so traumatized it might need to be put down, bringing the pet into the room to heighten the emotional weight. 

They also claimed Thomas Perez Sr.'s body had already been recovered from a nearby field, describing graphic details of the supposed discovery.

These statements were not true; tests showed no human blood, and the chemical detection can produce false positives.

Detectives drove Perez Jr. to construction sites and a donation bin, insisting these were spots where he might have hidden evidence. 

Such tactics, while legally allowed in many places, aimed to challenge his denials and prompt agreement.

Perez Jr. grew distraught, repeatedly asking about his father's location while officers shifted the narrative toward an accidental killing tied to his medications.

The involvement of the innocent dog in these claims added a layer of manipulation to the process, as People reported.

4) Breakdown leading to a false confession

The more the hours passed, the more dramatically Perez Jr.'s mental state began to deteriorate. At or around the 16-hour mark, he began hallucinating-people appeared in black and white, and he felt sharp pains like electric shocks shooting through his body.

He pulled at his hair, removed his shirt, and vomited from stress.

Detectives saw his apologies, "I'm sorry, Dad, I had no idea," as a guilty admission. He denied recalling any crime. Detectives took him through a hypothetical scenario: a dispute moving to blows and stabs with household items, followed by wrapping the body in a shower curtain.

Tired, disoriented from medication withdrawal and lack of sleep, Perez Jr. nodded along, later saying he thought that must be what happened because they repeated it so often. U.S. District Judge Dolly Gee decided that this constituted psychological coercion, given his vulnerability.

The session ended with Perez Jr. alone in the room, where he tried to harm himself using his shoelace, an act that was stopped when the shoelace broke.

This moment captured the toll of unchecked questioning on someone already fragile, as per People.

5) The delayed reunion and lingering harm

On August 9, some 30 hours after the report, police learned  Thomas Perez Sr. was safe at Los Angeles International Airport, waiting for a flight to visit his daughter.

He had left his phone at home and stopped by his brother's house without telling anyone.

Officers picked him up, questioned him at the station, and confirmed no harm had occurred; he had simply forgotten to update his family.

But they committed Perez Jr. to a 72-hour psychiatric hold in a hospital and directed phone staff to reject all incoming calls so the truth remained withheld from him for three entire days.

When  Thomas Perez Sr. spoke to his son by telephone, the relief was instant: Perez Jr. collapsed into tears, and they met shortly thereafter in a sobbing embrace.

The family reunited, but the damage lingered. Perez Jr. suffered from trauma, false memories, and trust issues for many years.

In 2019, he filed a lawsuit against the City of Fontana for coercion and false imprisonment, settling for $898,000 in 2024, according to the LA Times. 

Watch all the Dateline episodes available on NBC.