Brother did it again at Walmart

We were out shopping and I noticed he was pee dancing. I asked if he had to go and he said he did but didn't go to the bathrooms just kept shopping. Pretty soon he was actually grabbing and pinching himself threw his pants. I noticed a wet spot and asked if he had to go potty. He denied needing to go and we went to check out. I caught his reflection and he was holding himself hard. We walked past the bathrooms and paused but he didn't go in. When we got to the door to go out he made a noise and when I looked he was peeing his pants. I asked if he wet his pants and he just shrugged his shoulders.