(Newser) – A major breakthrough—or a deeply unfortunate coincidence? Police investigating the murder of Missy Bevers in Midlothian, Texas, obtained a search warrant after her father-in-law brought a bloody shirt to a local dry cleaner and told them the stains were animal blood, Fox News reports. An employee kept the XXL women's white shirt uncleaned and called police. The father-in-law, Randy Bevers, tells CBS 11 that the blood came from the family's Chihuahua, which was injured in a fight with another dog. Terri "Missy" Bevers, a 45-year-old fitness instructor and mother of three, was murdered in a church early on the morning of April 18 by a person dressed in SWAT gear who was captured on surveillance video.

Authorities are testing the shirt to determine whether the blood is human or animal. A source close to the investigation tells WFAA that a veterinarian has confirmed that Randy Bevers took the dog, which died of its injuries, to be treated. It had been attacked by another family pet soon after Missy Bevers' in-laws arrived in Texas from California. Other sources tell the station that investigators now believe that the attacker was not a burglar, but the person may have staged the killing to make it appear as if it happened during a burglary gone wrong.