Thu. May 12th, 2022

Man Runs Down Teen with His Truck, Mistaking That His Ex-Girlfriend Had an Affair with the Victim

On November 22nd, 2017, John Nieto chased down 18-year-old Cristian Dominguez-Aguilar in his truck, smashing him between his vehicle and the side of a 7-11 gas station. The motive was Nieto’s false belief that his child’s mother was having an affair with Cristian despite the fact that Nieto was no longer in a relationship with her. He was sentenced to 25 years to life in prison for the first-degree murder of Cristian.

Background Information

In 2011 when Elisabeth Mancilla was about 15 years old, she started dating John Nieto. By 2014 the couple moved in together and had a son. Sometime in 2017 Mancilla got a new job where she met her coworker Cristian Dominguez-Aguilar. Cristian was a friendly and very hard-working young man, excited to begin his American dream after immigrating to Fontana, California from Mexico only a year before. Mancilla and Cristian soon became friends, and she would often drive him to and from work.

Friends, family create memorial for 18-year-old Fontana man killed – Press  Enterprise
Cristian Dominguez-Aguilar

In October of 2017, Nieto discovered text messages between Cristian and Mancilla. Through these messages, Nieto obtained Cristian’s phone number and decided that Mancilla must be having an affair with Cristian. The text messages brought it to Nieto’s attention that Mancilla would give Cristian rides after work. More importantly, he found out where Cristian would get picked up and dropped off at. After seeing these messages and coming to the conclusion that Mancilla was cheating on him, which she wasn’t, he hit her causing her to break off the relationship and move out of their shared residence with their child.

In early November right after Halloween, using the phone number he got off of Mancilla’s phone, Nieto called Cristian and told him to “step off”, that he “better watch out”, that Cristian was going to “get himself into problems”, and that Nieto would “do whatever he had to for his family”. According to Nieto, Cristian expressed that he would not pursue Mancilla and that he understood why Nieto was worried. He also claimed that the conversation was just two guys talking to one another seriously without any yelling or arguing.

The Murder

Nieto attempted to call Mancilla on November 22nd, 2017, since it was her 21st birthday but she did not respond. That evening, Cristian texted his family saying that he was getting off of work late. His family member fell asleep while waiting for him to get off of work and woke up to see a text from him saying that he was getting a ride from someone. Despite this text, he did not arrive home. After going to his job in the morning, employees told the family member that he had left the night before as usual.

Shortly after Cristian’s family member was sent the text regarding Cristian finding a ride, a call came into 911 dispatchers for a severe hit and run. As it turns out, after Mancilla failed to answer Nieto decided to stake out a parking lot across from the 7-11 he knew Cristian would get dropped off at if he happened to be getting a ride from Mancilla that night. Nieto himself called this behavior stalking. Soon enough, Nieto sees Mancilla’s vehicle pull into the 7-11 parking lot, let Cristian out of the vehicle, and started to drive away.

ABC News Clip Showing Surveillance Videos that Captured the Murder

Nieto then drives his 2003 Chevy Silverado into the 7-11 parking lot behind Mancilla’s vehicle with his headlights off, which Mancilla notices and recognizes him. Cristian, unaware of what is going on, walks down the sidewalk towards the crosswalk thinking that he is going to finish his walk home from 7-11 as he always did when Mancilla would give him a ride. Nieto then does a U-turn which caused his tires to squeal before he attempted to hit Cristian as he crossed the street. Mancilla slammed on her horn, alerting Cristian who managed to dodge Nieto’s truck. Cristian attempted to hide between two electrical boxes across the street from the 7-11 before being chased further, running back across the street towards the 7-11. Nieto turned his truck around again before squealing his tires again, gaining speed, and slamming into Cristian as he ran for his life, pinning him between the truck and a wall of the 7-11. The force of the impact bounced the truck backwards releasing Cristian who fell to the ground, completely crushing the engine compartment, and resulting in significant structural damage to the 7-11. Seconds prior Mancilla returned to the 7-11 when she saw Nieto chasing Cristian behind her.

FONTANA: Couple arrested after 18-year-old fatally run down by co-worker's  boyfriend in jealous rage – Riverside County News Source
Nieto’s Truck with Smashed Engine Bay

After the collision, Nieto fled from the scene only to return and presumably grab his keys before running again. Mancilla exited her vehicle, now parked in the 7-11 parking lot again, and went to where Cristian was hit. After seeing that Cristian was mortally wounded, she returned to her vehicle, found Nieto, and brought him back to her house with their son. Although Cristian was clinging to life when authorities arrived, he died within minutes due to multiple blunt force injuries.

Statements to Police

With the help of CCTV from the area as well as statements made by Cristian’s family, authorities were able to get Nieto and Mancilla into custody the next morning on Thanksgiving day. After first claiming he didn’t remember what he did and that he never seen teen before, Nieto told officers he simply “wanted to fucking run Cristian over”. The reason was that he thought that Mancilla, who had broken up with him a month prior, was cheating on him with Cristian.

Elisabeth Mancilla

He stated that after Mancilla failed to answer his calls that he had a feeling that she would be dropping Cristian off at the 7-11 that day and that he thought “fuck it, I’m ruining Cristian’s Thanksgiving and fuckin’ holidays. Fuckin’ kill him”. When he saw her pull up and him get out of the vehicle, he stated that he “just went crazy and like just furious and I don’t know what the fuck I did. I just wanted to fuckin’ kill him.” Nieto recalled the situation, including Mancilla honking her horn allowing Cristian to dodge his truck, as well as the directions Cristian ran in an attempt to escape. When Cristian changed directions for the last time, Nieto stated he “just got on top of the curb” and “said fuck him, I’m just going to run him over”. 

Fontana teenager dies after being struck by vehicle driven by jealous  suspect, police say | News |
John Nieto

He continued to explain what happened and said “so I got on top of the curbs and then I just went this way and he started running this way, so I guess I just caught up to him. I just went on top of the curbs again.” After hitting Cristian, Nieto said he “just bounced”. When asked how fast he was going when he hit Cristian, Nieto stated that he didn’t know how fast he was going but that he pressed the gas pedal “all the way down” and “floored it” until he hit the wall.

He claimed to investigators that he wasn’t sure if he had hit Cristian or not when he collided with the wall, but that he “didn’t really care if Cristian died or not, just fucking hit him and that’s it”. When it was confirmed to him that Cristian had infact died, Nieto said “well fuck it, he looked for it, man”. Through the police interview Nieto stated that he didn’t regret his decision and that Cristian deserved it, going so far as saying that he would tell his son the truth about what had happened and say “yeah, fuckin’ I did it and I don’t regret it, you know?”


John Nieto was convicted of first-degree murder and sentenced to 25 years to life in prison in 2020. A clinical and forensic psychologist testified on Nieto’s behalf saying that Nieto had below average IQ and impulse control problems. The psychologist also noted severe substance abuse including the use of methamphetamine. Elisabeth Mancilla was charged as an accessory after the fact because instead of rendering aid to her friend and coworker, she picked up Nieto and brought him to her house. She was sentenced to 150 days in jail, allowing to leave on certain days for work. Mancilla and Nieto’s child was put into state care after their arrest. Mancilla has since been released, and Nieto is up for parole in 2037.

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