The birthday group had just finished tubing on the river—a favorite Texas pastime in the summer heat—before the physical attack, which included punching and shoving, left at least two members of their group injured. In video recorded of the incident, someone can be heard yelling “white power.”

“I am afraid to go back,” one victim told the Texas Observer. “I definitely won’t go back, and if anyone I know is planning to, I will probably tell them what happened to me to discourage them from going.”

Members of the birthday group reported the incident to police, and local law enforcement from the Caldwell County Constable’s office arrived on the scene after the incident and arrested one person, Todd Jeremy Christian, a 45-year-old with an Austin address, on Class A misdemeanor charges for assault causing bodily injury, according to a police report the Observer obtained via a public information request. The report categorized the assault as a gang-related crime motivated by “Anti-Multi-Racial Group” bias.

While only Christian was arrested, video evidence shows at least eight people were involved in the apparent assault on the group of family and friends. Of those eight, the Observer and Bellingcat have identified five—including Christian—as members or supporters of the Aryan Brotherhood of Texas (ABT), a white supremacist prison gang founded in the 1980s that is unrelated to the original Aryan Brotherhood.