Savanah Soto's heartbreaking case has experienced a big development. 

Three individuals have now been arrested in connection with the murders of the pregnant 18-year-old and her boyfriend Matthew Guerra, 22, who were found dead in a car on Dec. 26 with gunshot wounds.

More than a week after 19-year-old Christopher Preciado and his father Ramon Preciado, 53, were taken into custody in connection with the murders, Myrta Romanos, Christopher's stepmother, has been arrested. San Antonio police have charged Myrta, 47, who was arrested Jan. 17, with tampering with evidence, abuse of a corpse and altering, destroying or concealing evidence of a human corpse while announcing her arrest, according to ABC News.

In the early hours of Jan. 4, Christopher and Ramon were arrested by San Antonio police. NBC News reported at the time that Christopher was charged at the time with capital murder while his father was charged with abuse of a corpse for allegedly helping to move the bodies. As of Jan. 18, per ABC News, both father and son have been charged with of a corpse and altering, destroying or concealing evidence of a human corpse.

E! News has reached out for a statement from the attorneys for the three individuals but has not yet heard back.

Lt. Michelle Ramos shared, according to ABC News, that surveillance footage allegedly depicted Myrta leaving the family's home in black truck on the night of the murders and then returning with Christopher and Ramon in the vehicle. 

San Antonio Police Chief William McManus also reportedly shared, per ABC, that they recovered a firearm in the Preciados' home which was believed to be the murder weapon, which Myrta reportedly has now claimed as belonging to her.

In a news conference on Jan. 4, following the arrests of Christopher and Ramon, NBC News reported that detectives believed the deaths to be related to a "narcotics deal that went bad."

Savanah's family first alerted police on Dec. 24 that the Texas teen was missing after she missed a medical appointment to induce labor the previous day. Leon Valley Police issued a CLEAR Alert for Savanah on Christmas day, which included details about the 2013 gray Kia Optima she was believed to be using. 

Per police, Savanah's body was found alongside Matthew's two days later in that car parked at an apartment complex in northwest San Antonio. An individual had recognized the car and alerted Soto's family, who then contacted law enforcement. It was believed by police Savanah and Matthew been dead for three or four days at the time their bodies were found. 

"She was a good girl, she didn't deserve to go this way, especially with her baby," Savanah's grandmother Rachel Soto told CBS local affiliate KENS on Dec. 26. "He was an innocent child, nobody deserved this."

(NBC News and E! News are both part of NBCUniversal.)

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