Juan Ignacio Blanco  


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A.K.A.: "The Killer of Cumbres"
Classification: Murderer
Characteristics: Angered because his former girlfriend ended their relationship
Number of victims: 2
Date of murders: March 2, 2006
Date of arrest: 4 days after
Date of birth: 1984
Victims profile: Erick Peña Coss, 7, and María Fernanda Peña Coss, 3 (the brothers of his ex-girlfriend)
Method of murder: Stabbing with knife / Strangulation
Location: Monterrey, Nuevo Leon, Mexico
Status: Sentenced to 138 years in prison on October 11, 2011

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Diego Santoy Riveroll is a Mexican university student who is accused of stabbing his ex-girlfriend, Érika Peña Coss, and killing her two young siblings in the City of Monterrey on March 2, 2006. He was captured by police on March 7, 2006, at a roadblock in Oaxaca.

The Case

According to Érika, she had broken-up with Diego for personal reasons, but he kept calling and seeking her, unable to accept it. In March 2, 2006, she woke up early in the morning and found Santoy inside the house wearing a mask. She said he silenced her and started beating her with a hammer in the parietal.

He told her he had already killed her two little siblings and the servant was about to die from a drug overdose. He supposedly laid by her side, claiming he wanted to die next to her, but after thirty minutes nothing happened. This was later completely refuted by Diego himself. Then, he asked her to stab him, which she refused to do, so he threatened to kill her and then commit suicide to "catch up" with her. He proceeded to stab her in the neck and the back. Érika was almost dead when Santoy left.

Allegedly badly hurt- since later it was stated that her injuries were severe and required a six hour surgery to save her life- she crawled to the office in the back of her house and asked the secretary to call for an ambulance. Diego had indeed killed her younger siblings and had badly beaten the servant. While all of this was happening during a lapse of five hours, during which Azura, one of Érika's older sisters, assured she didn't know what was going on.

Nevertheless it has been proved that if all the above statements had happened, she would have heard something. Four days later Santoy was captured by the police at Oaxaca, where he was found in a bus along with his brother.

While imprisoned, Santoy confessed to the murders confirming Érika's story. However, after a few weeks he retracted the confession stating that he was forced by the officers to make up the whole story. His version of the murders points Érika as the killer. According to Diego, he had a sexual encounters with Erika's mother. He also claimed that Erika's father offered him and his daughters marijuana.

Another statement that he has mentioned is that he was sure the killed children were of a other father. That, along with many other accusations and rumors involving abortion and family fights, have been made to accuse Erika as his accomplice.

In his confession, she wanted to kill her siblings in order to take revenge on her mother and because of material matters, since they were born to a multimillionaire, owner of a television company. Santoy said she called him a day before and asked him to meet at her house at 4:00AM, as they usually did since her mother was out of town. Once there, she asked him for help to exact revenge upon her mother by killing her younger siblings.

He described to the authorities the way she stabbed her little brother and asphyxiated her sister with a rope. After that, they made a "suicidal pact" which was violated by both. Erika allegedly asked Diego to kill her, kidnap the servant, who was locked in the bathroom at the moment, and kill himself by throwing both himself and said servant from the Puente Atirantado. He tried to hit her in the head with a hammer but didn´t the courage to hit her hard enough. Then he "stabbed" her (Now it is known that her injuries were so severe that she most probably would have died) and was about to do as she told him. But then he declared that he lacked the courage to kill the servant and released her from her imprisonment and even gave her change to take a bus.


At the very beginning of the case, Santoy was seen as the sole suspect of the crime, but then the focus of the media changed to include the Peña Coss family too. The public appearances of the Peña family revealed conducts typical for a "victim", as many psychologist have commented on the case.

Many of them asseverate that in a case of that nature in which a surviving victim had a relationship with the aggressor, the reaction would be feeling angry against the aggressor. This was their current position.

On the other hand, the assertions they've made, such as Erika's father's affirmation of "Diego was crazy because of the stars" and "I saw it all coming and warned Erika; 'This boy is going to kill you' " weren't quite helpful. None of them has been seen as "trustworthy" in any of the interviews since they often contradict each other, specially the exact time of the crime, as Erika constantly changed her allegations as her previous ones claimed she woke up at 7:30AM, as opposed to her latest declarations that say it was at 12:00PM, the day of the crime.

Also, both Erika and the servant claimed to have seen Diego holding a gun and having a mask covering his face. Neither the gun, the mask nor the actual weapons that were used have been found. Thus this, is the fact that a hit inflicted by a hammer should be able to kill someone, and someone cold enough to kill two defenseless children should be able to kill the source of is assumed rage.

Another fore mostly incongruous statement in all of her acknowledgments is the appearance of the secretary. Erika firstly said that she "crawled" into her office -which was located in her house, as the secretary worked for Teresa Coss- and pleaded her to call an ambulance.

Contrary to that, Diego declared that he himself offered Erika to call an ambulance when he was infructuously trying to kill her. Yet, the secretary told the authorities that Erika came "normally walking into her office" and "casually asked her to call an ambulance" and waited for its arrival by her side, telling her supposed details on what had happened. It is also suspicious that she was already out of the hospital only thirteen days after the crime was committed.

In January 2007, Santoy confronted the whole Pena family, the servant and the secretary during a trial. During said confrontations it was made public many of the above statements on the family life-style. Santoy once again accused her of being the killer and asked her family to tell the truth about the case.

The Pena Coss family still denies the allegations and insist it was Diego who killed the children, while many local Santoy supporters gathered outside the prison, claiming he is innocent and denouncing Érika.


Uncertain as it is, many people claim that the children's mother, Teresa Coss has engaged in sexual relationships with influent people being Aldo Fasci, Assistant State Prosecutor.

Media attention

Santoy has gained notoriety due to high levels of media interest in the case and the even higher rarity of the case. He has been nicknamed el asesino de Cumbres (the murderer of Cumbres), Cumbres being the area of Monterrey where the killings happened.



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