A man arrested in the fatal stabbing of an elderly Bay Area resident outside his home, one day after being released from jail, has been identified by federal officials as an undocumented migrant from Venezuela.
Marcos Iriarte-Valdez, 36, is accused of killing 68-year-old Todd Stewart on the front lawn of Stewart’s Martinez home last week. Surveillance video reportedly captured the violent attack.
The Department of Homeland Security said Tuesday that Iriarte-Valdez is a “Venezuelan illegal alien” and alleged that the killing took place “in sanctuary California.”
“[Governor Gavin Newsom] must NOT RELEASE this murderer from jail and turn him over to us so we can REMOVE him from our nation,” the department wrote in a post on X.
Iriarte-Valdez was already facing legal trouble and had been on pretrial release in connection with a residential burglary case when he was jailed last Tuesday for allegedly violating the conditions of his home-detention monitoring.
The following day, a Contra Costa County Superior Court judge ordered his release on his own recognizance and referred him back to home detention.
Less than 24 hours after that decision, Stewart was dead.
Iriarte-Valdez had been on pretrial release in connection with residential burglaries that took place April 29 in Orinda.
Martinez Police Chief Andrew White said the suspect apparently did not even have his home-detention monitoring equipment placed on him until Friday, the day after Stewart was killed.
Iriarte-Valdez was arrested Friday evening at his home in the 1600 block of Ashwood Drive on suspicion of murder.
He is being held on $1.1 million bail.
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Police said there was no known connection between Iriarte-Valdez and Stewart.
Stewart had been working on a project in his garage before the attack, neighbors said.
The eruption of violence left Stewart’s neighbors stunned.
“I’m still processing because I still expect to see him over the fence,” neighbor Galina Pasternak told KTVU. “It’s nowhere as bad as his family, because they lost their father, his wife lost her husband. They finally were spending more time together because they were retired. They were traveling.”
Investigators quickly zeroed in on the suspect using surveillance footage, automated license-plate recognition technology and tips from residents who recognized the vehicle.
“Through using automated license plate recognition technology, we were able to locate what ultimately became that vehicle and understand kind of where it had been,” White said. “Simultaneously, we were receiving tips from the community from people who recognized the vehicle.”
Cops eventually tracked Iriarte-Valdez to his apartment complex and arrested him without incident.
His criminal record also includes an October 2025 arrest in Contra Costa County for DUI of alcohol and hit-and-run causing property damage, according to county booking records and police statements.
Following the alleged killing, Martinez police booked Iriarte-Valdez on suspicion of murder along with a secondary charge alleging he committed a felony while released on his own recognizance.
