FONTANA: Couple arrested after 18-year-old fatally run down by co-worker’s boyfriend in jealous rage

FONTANA — Officials say jealousy over a girl led to the intentional hit and run of a Fontana resident. The victim died after being transported to an area hospital, Wednesday, Nov. 22. The fatal incident happened at a 7-11 on the 17700 block of East Foothill Boulevard, on the northeast corner of Alder Avenue, in Fontana.

Christian Dominguez died after officials say he was intentionally run down by his co-worker’s boyfriend. Dominguez family photo

San Bernardino County Coroner officials later identified 18-year-old, Cristian Dominguez-Aguilar, of Fontana. According to a coroner’s release, Dominguez was pronounced dead by emergency room staff at 7:55 p.m., about 35 minutes after he was run down.

After an investigation, officers located and arrested John Nieto, 20, of San Bernardino and Elisabeth Mancilla, 20, of Rialto.

Nieto was booked into West Valley Detention Center on suspicion of murder and Mancilla was booked on suspicion of being an accessory to murder for helping her boyfriend flee the scene of the deadly incident.

The investigation began about 7:15 p.m., when Fontana Police and Fire personnel and American Medical Response medics responded to the hit and run, after a witness called 911 to report that a pickup truck had smashed into the 7-11, critically injuring a pedestrian.

When emergency first responders arrived at the location, they found a white Chevy Silverado pickup truck with heavy front-end damage near the back corner of the 7-11. They also located the victim, who was later identified as Dominguez.

Paramedics attempted to provide Dominguez life-saving measures before AMR medics rushed him to Arrowhead Regional Medical Center in critical condition. He later succumbed to his injuries and died at the hosital.

As the investigation was unfolding, Fontana PD officers obtained closed-circuit, surveillance footage from the 7-11 that captured the deadly incident. (See surveillance video footage of incident below.)

Based on the surveillance video footage, officials determined the driver of the pickup truck, who was later identified as Nieto, attempted to run down Dominguez as he was walking to his residence.

After plowing into the victim and 7-11 convenience store, the alleged suspect, John Nieto fled from the scene with his girlfriend, Elisabeth Mancilla. William Hayes photo

After initially missing Dominguez, Nieto turned his truck around and chased the fleeing man across the 7-11 parking lot before striking the victim and smashing into the 7-11.

Based on the circumstances, Fontana PD detectives responded to the scene and assumed the investigation.

They were assisted by forensic technicians from the department’s Field Evidence Unit and San Bernardino County Coroner’s officials.

During their investigation, officials learned Dominguez occasionally received a ride home from work by a female co-worker, later identified as Mancilla. Detectives also learned that Mancilla normally dropped the victim off at the 7-11 where the deadly incident happened.

According to a Fontana PD press release, Nieto suspected Dominguez and Mancilla – who is his girlfriend and the mother of his child – were involved in a relationship. Based on their investigation, officials have said they believe no such relationship existed.

Knowing that Mancilla normally dropped Dominguez at the 7-11, Nieto waited across the street for Mancilla to drop of Dominguez.

According to officials, as Dominguez exited Mancilla’s car and crossed the street on foot to walk to his residence – which was less than a block from the convenience store – Nieto used his vehicle to try to run the victim over. Although Nieto missed Dominguez the first time, he turned around and continued to chase the victim in his vehicle across the 7-11 parking lot.

After being fatally run down many of the victim’s personal belongings, including his shoes and backpack, were found scattered across the convenience store’s parking lot. William Hayes photo

As Dominguez was fleeing from Nieto towards the rear of the 7-11, the alleged suspect ran the victim over.

Officials said Nieto was going so fast he lost control of his truck and plowed into the 7-11 convenience store.

The impact destroyed and disabled Nieto’s truck and left Dominguez critically injured and dying in the parking lot.

After Nieto’s vehicle was disabled, the alleged suspect fled from his truck and was picked up down the street by Mancilla, who officials said saw the entire fatal encounter.

According to officials, although Mancilla witnessed the incident and saw that Dominguez was critically injured, she never called police or attempted to render aide to her dying co-worker

After picking up Nieto, officials say Mancilla drove him to his residence in San Bernardino. She then drove to her home in Rialto.

Officials investigating the fatal hit and run documented, photographed and collected numerous items of evidentiary value; including numerous personal items belonging to the victim, which were spread across the parking lot and behind the 7-11.

Officials located and apprehended both alleged suspects at Mancilla’s Rialto residence, at 10 a.m. the next morning. After interviewing both subjects, officers arrested the couple.

An online jail records search revealed Nieto remains in custody and is being held without bail. His next court date is scheduled at Rancho Superior Court, Nov. 28.

Fontana police officers search for evidence related to the deadly hit and run. William Hayes photo

After Dominguez’ was killed, family members were left reeling at the victim’s senseless death.

The victim’s cousin, Liliana Dominguez later told the San Bernardino County Sun, “All I can think about him right now is his smile. His big, happy smile. He was a really happy young man and I can’t believe he’s gone.”

“He was a good, young man,” Liliana continued. “He was going to college and going to work. He was a good person.”

In the wake of his brother’s death, Armando Dominguez created a gofundme account to help raise funds to offset the victim’s burial cost and other expenses. After the first day, the fundraiser had raised just over $1,200.

On the fundraiser’s page Armando said Dominguez “was always laughing, smiling and helping others.” He also said people who knew the victim knew what a great person he was.

Those wishing to donate to the victim’s fundraiser can find more information on the family’s gofundme page.

Anyone with information related to this investigation or who witnessed the fatal incident is encouraged to contact Fontana Police Detective Jason Coillot at (909) 350-7700. Callers can refer to incident file number 17-21044 and can remain anonymous.

Click any image to open full-size gallery.

During their investigation, officials obtained 7-11 surveillance video footage that showed much of the fatal hit and run. (WARNING – video contains shocking images not suitable for younger viewers and viewer discretion is advised.)


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Trevor Montgomery, who recently moved from Riverside County to Shasta County, runs Riverside County News Source and Shasta County News Source. Additionally, he writes for Riverside County based newspapers Valley News, The Valley Chronicle and Anza Valley Outlook as well as Bonsall/Fallbrook Village News in San Diego County.

Trevor spent 10 years in the U.S. Army as an Orthopedic Specialist before joining the Riverside County Sheriff’s Department in 1998. He was medically retired after losing his leg, breaking his back and suffering both spinal cord and brain injuries in an off-duty accident.

During his time with the sheriff’s department, Trevor worked at several different stations, including Robert Presley Detention Center, Southwest Station in Temecula, Hemet/Valle Vista Station, Ben Clark Public Safety Training Center and Lake Elsinore Station, along with other locations.

Trevor’s assignments included Corrections, Patrol, DUI Enforcement, Boat and Personal Water-Craft based Lake Patrol, Off-Road Vehicle Enforcement, Problem Oriented Policing Team and Personnel/Background Investigations. He finished his career while working as a Sex Crimes and Child Abuse Investigator and was a court-designated expert in child abuse and child sex-related crimes.

Trevor has been married for more than 27 years and was a foster parent to more than 60 children over 13 years. He is now an adoptive parent and has 13 children and 14 grandchildren.