Homicide Investigation Begins After Inmate at the West Valley Detention Center is Killed by Cellmate 

January 22, 2026 - San Bernardino County Sheriff’s Department officials report that on Monday, January 19, 2026, at about 11:12 p.m., deputies found inmate Zacarias Joseph Ruiz unconscious in his cell with obvious trauma. Deputies and jail medical staff performed lifesaving measures until emergency medical personnel arrived and transported Ruiz to a hospital. Ruiz was pronounced deceased the following day.   

The Sheriff’s Specialized Investigation Division – Homicide Detail responded and assumed the investigation.  Through investigation, detectives determined Ruiz and his cellmate, Isaiah Mark Bailon, were involved in a physical altercation before deputies found Ruiz.

Bailon has been in custody since December 31, 2025, when Hesperia Station deputies arrested him for attempted murder and robbery. Bailon was supplementally booked for murder.

Ruiz was arrested on May 5, 2025, for criminal threats and domestic violence and remained in custody until his death. An autopsy will be conducted to establish a manner and cause of death.

This investigation is ongoing and anyone with information related to this case is asked to contact the Homicide Detail at 909-890-4904.  Callers wishing to remain anonymous should contact We-Tip at 1-800-78-CRIME (27463) or go to www.wetip.com.

DATE:  January 19, 2026, 11:12 p.m.
INCIDENT: PC 187 -Murder – In-Custody Death Investigation
LOCATION: West Valley Detention Center, 9500 Etiwanda Avenue, Rancho Cucamonga
SUSPECT(S): Isaiah Mark Bailon, 26-years-old, Resident of Barstow
VICTIM(S): Zacarias Joseph Ruiz, 38-years-old, Resident of San Bernardino
Refer:  Detective E. Badillo
Station: Homicide Detail 
Phone No. 909-890-4904
Case No. DR# 342600169  H# 2026-006

Source: San Bernardino County Sheriff’s Department