Four Arrested in Connection with Fatal Assault at Sonoma Plaza

Four suspects have been taken into custody on charges of murder and conspiracy following a violent assault at the Sonoma Plaza that resulted in the death of a 64-year-old Sonoma resident.

On Monday, September 7, 2026, at approximately 10:30 PM, patrol officers responded to reports of an injured individual near the Italian Fountain within the Sonoma Plaza. Upon arrival, officers located a 64-year-old male victim lying unconscious on the ground. First responders rendered immediate medical aid, and the victim was transported to a regional trauma center in critical condition.

Despite intensive medical treatment, the victim succumbed to his injuries early in the morning on Sunday, September 13, 2026. The victim has been identified as John Francis Avila, a Sonoma resident.

Sonoma County Sheriff’s Office Violent Crimes Investigation Detectives launched a comprehensive investigation into the incident, utilizing area surveillance footage, Automated License Plate Readers, physical evidence, and witness statements. Investigators determined that four individuals physically assaulted the victim, causing the injuries that ultimately led to his death.

Following the investigation, detectives identified and located all four suspects. They were arrested without incident and booked into the Sonoma County Main Adult Detention Facility on Sunday (9/14/26).

Suspect Information and Charges:

• Cristian Vargas Collado, 20 year old Sonoma resident: Booked on PC 187(a) Murder, and PC 182(a)(1) Conspiracy to commit murder.
• Augustine Rossi, 20 year old Sonoma resident: Booked on PC 187(a) Murder, and PC 182(a)(1) Conspiracy to commit murder.
• Thomas Griego, 21 year old Sonoma resident: Booked on PC 187(a) Murder, and PC 182(a)(1) Conspiracy to commit murder.
• Anthony Kirk, 28 year old Sonoma resident: Booked on PC 187(a) Murder, and PC 182(a)(1) Conspiracy to commit murder.

The City of Sonoma, the Sonoma Police Department, and the Sonoma County Sheriff’s Office would like to express our condolences to the family of John Avila.

We would also like to thank the community members that provided information about the incident as well as the numerous businesses around the incident who provided security footage.  While the details of the investigation cannot be disclosed at this time, the identification of the suspects was only made possible using the City of Sonoma’s Automated License Plate Reader (ALPR) technology.  Without access to our ALPR data for this criminal investigation, identification would have been delayed if not nearly impossible.

The Sonoma Police Department is a contract law enforcement agency under the Sonoma County Sheriff’s Office.  This relationship allows the City of Sonoma to have the assistance of the staffing and experience of the Sheriff’s Office Investigation units.  We appreciate the hard work and investigative professionalism of the Violent Crime detectives, Crime Scene detectives, Narcotic Investigation detectives, and Property Crime detectives.

This remains an active and ongoing investigation. Law enforcement urges anyone who witnessed the incident, has video footage, or possesses additional information regarding this event to contact the Sonoma Police Department 707-996-3601.

Press Release Prepared by Brandon Cutting, Chief of Police, Sonoma Police Department.