Monroe, WA man charged with murder, child assault after lengthy investigation
Man arrested in 2025 death of 2-year-old child
A Monroe, Washington man is in custody, accused of killing a two-year-old girl and abusing her five-year-old brother.
SNOHOMISH COUNTY, Wash. - A 27-year-old Monroe man was arrested and charged with the second-degree murder of a 2-year-old girl and the second-degree assault of her five-year-old brother.
According to charging documents, Samuel Adonis Cardoza-Menjivar was taken into custody on Tuesday evening by members of the Pacific Northwest Violent Offender Task Force at a motel on Old Owen Road in Monroe. On Wednesday, the Snohomish County Prosecutor’s Office filed formal charges in Snohomish County Superior Court. Prosecutors also requested $1 million bail, which was granted.
The arrest concludes an intensive eight-month investigation led by the Snohomish County Sheriff’s Office Special Investigations Unit (SIU) into an incident that began in late 2025.
"An extremely tragic incident here," said Courtney O’Keefe, public information officer for the sheriff's office.
The initial incident and emergency response
On the morning of December 1, 2025, Cardoza-Menjivar was the sole adult present, a 2-year-old girl and her 5-year-old brother, at a home on Avenue J in Snohomish. Cardoza-Menjivar was the then fiancé of the children's mother, who was at work at the time.
According to court records, Snohomish County Sheriff’s deputies received 911 calls shortly before 8:18 a.m. When first responders and Snohomish County Sheriff's deputies arrived at 8:22 a.m., they found the 2-year-old girl unconscious, pulseless, and fully clothed with dry hair.
"Upon arrival, medics did do extensive CPR before transporting her to Providence Regional Medical Center. From there, the 2-year-old girl was transported to Seattle Children’s Hospital," said O’Keefe.
Despite medical intervention, the little girl suffered severe anoxic brain injury, according to court documents. She died six days later, just short of her third birthday
(FOX 13 Seattle)
Conflicting stories and medical findings
Cardoza-Menjivar initially told responding deputies and detectives that the toddler fell while in the shower and hit her head.
However, medical professionals at Seattle Children’s Hospital quickly alerted law enforcement that the toddler’s injuries were inconsistent with a ground-level fall.
"The hospital staff had done a full medical evaluation on her and her injuries were consistent with non-accidental head trauma," said O’Keefe.
Following a comprehensive autopsy, which included neuropathology and histology consultations, the Snohomish County Medical Examiner’s Office concluded in March 2026 that the girl’s cause of death was blunt head trauma and certified the manner of death as a homicide.
Evidence of abuse against five-year-old brother
O’Keefe said Child Protective Services (CPS) removed the 5-year-old brother from the home, "to ensure that [he] was safe throughout the duration of the investigation." Court documents state that medical evaluations of the young boy revealed bruising on his neck, which child abuse experts identified as highly consistent with strangulation finger marks, as well as grip marks on his arms.
In a recorded interview with a Child Forensic Specialist on December 4, 2025, the boy described what happened inside the home, stating that Cardoza-Menjivar attacked his sister, choking her, grabbing her limbs, and slamming her down. The young child also demonstrated how Cardoza-Menjivar grabbed his own neck.
Investigation timeline
While detectives identified red flags early in the investigation, O’Keefe said building a case required months of forensic work. Because Cardoza-Menjivar initially claimed the toddler's injuries were the result of a fall in the shower, investigators could not rely on initial statements alone. O’Keefe said they had to wait for specialized medical evaluations, neuropathology consultations, and the final toxicology and autopsy findings from the Snohomish County Medical Examiner's Office.
Regarding the lengthy timeline, O’Keefe explained, "A lot of that had to do with medical examiner report, autopsy medical, forensic testing, everything that had to be done in order to evaluate her injuries for detectives to determine what happened here."
Specialized pediatric child abuse experts at Seattle Children's Hospital and state forensic teams worked to meticulously document the extent of both children's injuries to scientifically disprove the suspect's timeline of events. O’Keefe explained that the length of the eight-month investigation was necessary to ensure every piece of physical and medical evidence was fully vetted.
Court proceedings and $1 million bail request
Court documents filed by the prosecutor’s office outline the State's request for $1 million bail, which was granted in court on Wednesday. In the charging documents, prosecutors argued that Cardoza-Menjivar poses a "significant danger to the community" and a substantial flight risk, noting his lack of a permanent address, previous domestic violence history, and family connections in Mexico.
In April 2026, Cardoza-Menjivar had previously pleaded guilty to Fourth-Degree Assault (Domestic Violence) following a September 2025 incident where he attacked the children's uncle with a butter knife.
In this latest case, Cardoza-Menjivar was charged with second-degree murder and second-degree assault of a child.
Cardoza-Menjivar is being held in the Snohomish County Jail awaiting his formal arraignment.
O’Keefe said while the sheriff’s office has the suspect in custody, the SIU will continue working to close this case.
"They are investigating crimes that involve children, our most vulnerable people in Snohomish County," said O’Keefe. "And they are dedicated to getting justice and holding these people accountable for what they’ve done."
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The Source: Information in this story comes from original reporting by FOX 13 Seattle reporter Franque Thompson.