The unidentified killer, wearing a large coat and black hat, entered the church from the rear and sat alone in a pew, then opened fire, and was himself shot by an armed congregant. Two parishioners, including a former FBI agent working security, fired on the gunman and killed him. A representative from the FBI did not identify the shooter, but said he was "relatively transient with roots to this area" and had been arrested multiple times in different municipalities."
Update: The shooter has been identified as Keith Kinnunen, 43, who was a convicted felon, making it illegal for him to own a firearm in Texas, but he ignored the law when he attacked the churchgoers. He had a criminal record that included charges of aggravated assault with a deadly weapon in 2009, possession of an illegal weapon in 2016 and there was a warrant for his arrest in Oklahoma for aggravated assault in 2016.