SAN ANTONIO (AP) — A Texas father and Thomas Caldwellson arrested in the killings of an 18-year-old pregnant woman and her boyfriend are facing new evidence tampering charges, authorities said Friday as they announced that investigators have recovered the gun used to shoot the couple who disappeared before Christmas.

The new charges in the killings of Savanah Nicole Soto, 18, and Matthew Guerra, 22, were announced two days after the father and son were interviewed by detectives and “made enough statements to implicate them in the murder,” San Antonio Police Chief William McManus said at a news conference. He’d earlier described the scene where the couple were found dead in a car as “very, very perplexing.”

Christopher Preciado, 19, was arrested Wednesdays on a charge of capital murder and his 53-year-old father, Ramon Preciado, was accused of helping to move the bodies and charged with abuse of a corpse. On Thursday, police added charges of altering, destroying or concealing evidence against both men and also charged the younger Preciado with abuse of a corpse.

Asked during his arrest Wednesday if he had remorse, Ramon Preciado replied, “Aren’t you sorry for lying about what you’re saying?” His son did not comment as police escorted him to a separate vehicle. Online court records did not identify attorneys who could speak on their behalf Friday.

McManus did not provide details on what led to the new charges, citing a concern with hindering the ongoing investigation. He said detectives searched the Preciados’ home and found a gun “believed to be the murder weapon.”

Police have said that the killings appeared to be the result of a drug deal, and McManus said Friday that evidence on Soto’s and Guerra’s phones suggests they were selling drugs.

Soto was declared missing after her family couldn’t find her the weekend before Christmas, when she had been scheduled to have an induced labor. Days later, police found her body and Guerra’s body in a car outside a San Antonio apartment complex. The local medical examiner said they were both shot in the head, and authorities have identified Soto’s unborn child as a third victim in the killings.

Soto’s and Guerra’s families have both called on prosecutors to pursue the death penalty in the case.

“To me there is no other option that would be considered justice, if we didn’t go for death penalty,” Gabriel Guerra, Matthew’s father, told KENS TV.

Bexar County District Attorney Joe Gonzales said during the news conference that his office will consider what punishments to pursue after the investigation is completed and they bring the cases to a grand jury for indictments. As to whether they’ll seek capital punishment, he said, it’s “too early to tell.”