A San Diego man who fatally stabbed his estranged wife in the Imperial Beach sheriff's substation parking lot in February pleaded guilty Wednesday to first-degree murder.
Marvin Dennis Duncan, 60, is due to be sentenced on July 26. He faces a stipulated 25 years to life in prison.
Shortly after 3:30 p.m. on Feb. 6, Duncan pressed an intercom button at a side door at the substation between the IB Fire Department and City Hall on Imperial Beach Boulevard, said sheriff's homicide Lt. Glenn Giannantonio.
When a deputy answered, Duncan, who was holding two toddlers, announced he had just killed his spouse, according to the lieutenant.
The mortally wounded victim -- Duncan's 36-year-old wife, Rocio -- was found lying on the ground on the west side of the substation. She died a short time later.
Duncan was detained for questioning and later arrested. The children, who were unharmed, were taken into protective custody. The motive was under investigation.