Police say an ongoing dispute between two coworkers escalated into a deadly confrontation at Northgate One Shopping Center.
SAN RAFAEL, Calif. — A 20-year-old Richmond man was arrested on suspicion of murder after police said an ongoing dispute between coworkers escalated into a fatal stabbing at a San Rafael shopping center Monday afternoon.
Justin Amilcar Gutierrez-Navarette was arrested in connection with the death of Mathew Ryan Lambdin, 27, of San Rafael, following a confrontation at a business in the Northgate One Shopping Center. San Rafael police said the two men worked together and had been involved in an ongoing dispute before the conflict turned physical on Oct. 12.
Police and firefighters were called shortly after 1 p.m. to the 700 block of Las Gallinas Avenue after a caller reported an unconscious man who appeared to have fallen. First responders instead found Lambdin suffering from an apparent stab wound. People at the scene had already begun providing aid, according to police. Paramedics continued lifesaving efforts and transported Lambdin to a hospital, where he later died.
Investigators initially did not know where the confrontation had occurred. Police said Lambdin’s clothing led detectives to determine that he worked at a business inside the nearby Northgate One Shopping Center. Authorities have not publicly identified the business where the two men worked or explained what prompted the dispute between them.
Police said their investigation determined that Lambdin and Gutierrez-Navarette had been involved in an ongoing disagreement that escalated into a physical confrontation Monday. During that confrontation, police allege Gutierrez-Navarette stabbed Lambdin. Investigators said Lambdin then left through the rear entrance of the business and made his way outside before collapsing near the Northgate Medical Dental Center on Las Gallinas Avenue.
Shortly after detectives began investigating the death, Gutierrez-Navarette contacted the San Rafael Police Department and arranged to surrender, authorities said. Police said he cooperated during an interview with detectives. Investigators later arrested him and booked him into the Marin County Jail on suspicion of murder. Subsequent reports said he remained in custody without bail.
The Marin County Sheriff’s Office Coroner Division publicly identified Lambdin on Thursday. Chief Deputy Coroner Roger Fielding said the official cause and manner of death remained pending while police and coroner investigations continued. Police have characterized the case as a homicide investigation but have not released additional details about the circumstances that preceded the coworkers’ confrontation.
San Rafael police said investigators have identified the people involved and are not searching for additional suspects. The department also credited bystanders who called 911 and provided first aid before emergency crews arrived.
The case remains under investigation. Authorities have not publicly disclosed the nature of the coworkers’ earlier dispute, and no final findings on Lambdin’s cause and manner of death have been announced.
Author note: Last updated October 16, 2026.