Authorities: Woman believed to have been stabbed, killed at IB sheriff's substation parking lot

59-year-old allegedly stabbed Rocio Duncan, 36

IMPERIAL BEACH, Calif. - A 59-year-old man was in custody Wednesday after confessing to stabbing his wife to death in the parking lot of the sheriff's Imperial Beach substation, authorities said.

Marvin Dennis Duncan was arrested Wednesday and booked into San Diego Central Jail on suspicion of one count of murder in the death of Rocio Duncan, 36, according to San Diego County sheriff's Lt. Glenn Giannantonio.

Around 3:40 p.m. Wednesday, a man -- later identified as Duncan -- walked up to a side door at the substation at 845 Imperial Beach Boulevard and pressed an intercom button, the homicide lieutenant said in a statement.

When a deputy opened the door, he saw a man who was holding two toddlers and who said he had just killed his wife, Giannantonio said.

Authorities said they believe the man stabbed the woman multiple times in the parking lot of the substation. Homicide investigators found the body at the back of the substation next to a white Nissan pickup truck.

"He just said it rather matter-of-factly that he'd just killed his wife," said sheriff's Lt. Glenn Giannantonio. "He complied with the deputies' demands and orders and put the children down. He had a knife in his waistband. Without even being asked or told to, he took the knife out and dropped it on the ground."

The victim was found on the west side of the substation lying on the ground and suffering from stab wounds. She was still breathing when deputies found her but died a short time later, he said.

The man was immediately detained at the scene and the children taken into protective custody, Giannantonio said. The children were not injured.

Court documents obtained by 10News stated that the suspect and the victim divorced last September. Six other court cases were found involving domestic issues. However, a San Diego police press release described the two as currently married and are residents of San Diego.

10News cameras captured a homicide detective and two sheriff's deputies arriving at Duncan's Valencia Park home.

Neighbor and friend Cesar Gonzales was shocked when 10News told him Duncan had turned himself in a few hours earlier.

"To be honest… it's pretty shocking, you know, because he was so like a family person," said Gonzales.

Gonzales told 10News that Duncan was former U.S. Navy and currently worked at the NASSCO shipyard, where he had been employed for the past 30 years. He described Duncan as a family man.

"He was talking about the kids most of the time because he wanted to have the kids… always wanted to have the kids," said Gonzales.

The motive for the slaying was under investigation.

Anyone with information about the case was asked to call homicide detectives at (858) 974-2321 or after hours at (858) 565-5200.

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