A 27-year-old Monroe man is facing second-degree murder and second-degree assault of a child charges after Snohomish County investigators say he killed his girlfriend's 2-year-old daughter and injured her 5-year-old son while the children were in his sole care. Samuel Adonis Cardoza Menjivar was arrested Tuesday, more than nine months after emergency crews were first called to a Snohomish home where the toddler was found unconscious and covered in bruises.
Snohomish County Sheriff's Office deputies responded to a residence in the 300 block of Avenue J in Snohomish on December 1, 2025, according to KIRO 7 News Seattle. A police report detailed that the 2-year-old girl was unconscious with extensive bruising around her eye, forehead, and behind her ears when first responders arrived, and fire personnel administered CPR on scene for approximately 40 minutes, as reported by The Daily Herald. The girl was first taken to Providence Regional Medical Center Everett before being transferred to Seattle Children's Hospital, where she died on December 7, 2025.
Injuries Called Inconsistent With a Bathroom Fall
Menjivar told investigators the toddler had fallen in the bathroom and sustained a head injury, but medical personnel concluded her injuries did not match an accidental fall. The Snohomish County Medical Examiner's Office officially determined in March 2026 that the child's death was a homicide caused by blunt force head trauma, per the same Daily Herald account. Detectives say the children were at home in Menjivar's sole care at the time, and that he also caused neck and arm injuries to the girl's 5-year-old brother.
Menjivar was dating the victim's mother at the time of the incident, the Herald reports. The nine-month gap between the initial 911 call and Tuesday's arrest reflects the scope of the investigation, which detectives built to connect Menjivar to both the girl's fatal injuries and the non-fatal injuries to her brother before seeking charges.
Arrest Made by Regional Violent Offender Task Force
The Pacific Northwest Violent Offender Task Force arrested Menjivar at a motel on Old Owen Road in Monroe on Tuesday, according to the Herald's reporting via KIRO 7. Formed in 2013, the task force operates as a cross-commissioned unit under the U.S. Marshals Service, combining detectives from the Snohomish County Sheriff's Office, the Washington State Department of Corrections, Mountlake Terrace Police, and Mukilteo Police, with participating officers holding Special Deputy U.S. Marshal authority to execute warrants. The unit recorded 206 felony arrests across the region in 2024, including an all-time high of 23 homicide suspects, according to the Lynnwood Times — the highest annual number of homicide apprehensions since the task force's 2013 inception.
Following his arrest, Menjivar was booked into the Snohomish County Jail. He is due in court Wednesday afternoon for an initial arraignment, with online court records tracking the preliminary appearance.
What the Charges Carry Under Washington Law
Second-degree murder in Washington is classified as a Class A felony carrying a potential maximum sentence of life imprisonment and a fine of up to $50,000, and it does not require proof of premeditation, according to Black & Askerov. The second-degree assault of a child charge tied to the 5-year-old boy is a Class B felony punishable by up to 10 years in prison and a fine of up to $20,000, and applies when an adult intentionally causes bodily harm to a child under age 13, per the same firm's explainer on Washington's child assault statute.
The case lands amid broader county-level trends in violent crime. Annual data compiled by the Washington Association of Sheriffs and Police Chiefs showed homicides in Snohomish County fell 43.7% in 2024 to 12 total murders, down from 21 in 2023, while overall violent crime dropped 5.4%, the Herald reported last year. That same reporting noted domestic violence accounted for nearly half of all crimes against persons statewide. Separately, the Sheriff's Office's Major Crimes Unit handled 177 active cases in 2023, including 29 homicides, with detectives specifically assigned to domestic violence and cold case files, according to the agency's own operational records.
