NBC 7 San Diego
Investigators cordoned off the parking lot outside the Imperial Beach sheriff's substation.
Sheriff's detectives are still looking for a motive behind a bizarre homicide Wednesday in the parking lot of their department's station in Imperial Beach.
They're not saying whether, or to what extent, the fatal stabbing was caught on surveillance video.
Or, if they’re following online data that raises further questions about the suspect’s true marital status.
While the killing otherwise might seem an open-and-shut case, it’s not often that someone surrenders and confesses to murder just moments after carrying one out.
Especially doing so right on law enforcement property.
Why, and what prompted all that, is still a mystery at this point.
At around 3:40 p.m. Wednesday, a man carrying two toddlers was arrested inside the Imperial Beach sheriff's station after telling deputies he'd just killed his wife outside in their parking lot.
Authorities say he then produced a knife from his waistband, and calmly laid it on the ground.
Sure enough, a woman was found slumped -- stabbed multiple times, but still breathing -- in the passenger's seat of a white truck.
She apparently died before paramedics arrived.
The truck is registered to a Marvin Duncan, 59.
His home in San Diego's Valencia Park was searched under a warrant.
Neighbors told NBC 7 that Duncan’s his wife recently died, and that another woman has since been seen living there.
Curiously, records from online databases show that the Social Security number of a Nicolasa Duncan -- deceased at the age of 54, as of last year -- has been used by a woman named Maria, listing two different surnames.
The victim has not been identified, pending notification of next of kin by the county medical examiner’s office.
So what was her relationship with Duncan?
"I don't have information as to their actual marital status,” Sheriff’s Lt. Glenn Giannantonio told reporters at a briefing Wednesday evening. “(Duncan) did say 'his wife'. But I'm not sure if they were still married or separated or what-have-you."
When asked if the children witnessed the knife attack, Giannantonio replied: "I don't know for sure … I was just in with the children. They seem fine. We have some professional staff members that are kind of playing with them and taking care of them. Paramedics were here and checked them out, and physically they seem to be doing okay."
So far, there’s no word as to when Duncan will be arraigned in court.
The two toddlers, whose ages and gender are being withheld, are in the custody of Child Protective Services pending a placement with suitable relatives.