The video at the link says the men were open carriers. The Texas carry permit is for both open and concealed carry.
According to a press release by the Tyler Police Department, 34-year-old Chad Boening approached a man and woman in the parking lot between FD's Grill House and Bed, Bath and Beyond. Police say he brought out a knife and threatened the woman saying “do you want to see her die.”
Police say that a father and a son saw the incident from their vehicle and confronted the man. Both men brought out their concealed handguns to subdue Boening.