A 34-year-old man from Missouri has been detained on suspicion of killing the mother of his child. She was found sitting upright in a chair in her home with a plastic bag affixed over her head. Karl Mayberry was apprehended on Wednesday and charged with first-degree murder for the 2021 death of 31-year-old Alvatyne Thomas, as indicated by court documents reviewed by Law&Crime.

The probable cause affidavit states that officers from the St. Louis Metropolitan Police Department responded on Dec. 27, 2021, to a home in the 4000 block of Oregon Avenue after a request for a welfare check was made.

First responders arrived at the location, entered the residence, and found an adult female, later identified as Thomas, already deceased with “a plastic bag taped around her head.”

“She had been shot in the back and had extreme swelling to her forehead, a severed ear and apparent defensive wounds on her hands,” the affidavit states. “She appeared to have had bleach poured over her body as well.”

During the ensuing investigation, officers said they learned from Thomas’ family that she had been in an abusive relationship with the father of her child, whom they identified as Mayberry. Investigators obtained and executed a search warrant on Thomas’ cellphone.

Love true crime? Sign up for our newsletter, The Law&Crime Docket, to get the latest real-life crime stories delivered right to your inbox.

The data obtained from her phone allegedly showed that Thomas had been texting with Mayberry shortly before her death. In the text messages, she allegedly told Mayberry that she was at her house and was about to go to sleep.

In an interview with detectives, police said Mayberry claimed that he was at work at the time Thomas was killed.

“However, officers interviewed multiple co-workers, who stated the Defendant had disappeared for hours during the timeframe in question,” the affidavit states. “Officers also learned that, when the Defendant appeared again, he was in different clothes and appeared emotionally distraught.”

A search warrant was obtained for Mayberry’s cellphone as well as his social media. On the phone, authorities said they found messages sent by Mayberry to another unnamed person just after Thomas’ murder. In the messages, Mayberry wrote that Thomas had been “found dead in the kitchen with a plastic bag wrap around her head.”

According to authorities, Mayberry’s message about the details of Thomas’ murder were sent “prior to police releasing this accurate information to anyone.”

In addition to the messages, Mayberry also allegedly performed several incriminating internet searches around the time of Thomas’ death. Those searches allegedly included “first degree murder defenses” and “can he say she say be used against a person for murder in Missouri,” among others.

Mayberry also sent a text message to a criminal defense attorney inquiring how much it would cost “to defend a murder,” according to the affidavit.

Mayberry is currently being held at the St. Louis City Justice Center without bond, jail records show. Court records show he was on federal probation at the time of Thomas’ death due to convictions for assault and being a felon in possession of a firearm.

He made his initial appearance in court on Friday afternoon.