Was passing by and needed try on some winter boots...

Was passing by and needed try on some winter boots to figure out my size for future reference and for a friend who has the same size as me and was going to buy boots soon. I asked a sales associate to help me out. I had an idea already to what size I must be so it legit took only 5 minutes and I thanked the sales associate and told him I would be buying next time. He got mad at me and told me I wasted his time, making me feel bad and apologizing to him, to which now that I think about it, I really shouldn't have. I also tried to ask him a question and he answered in a way as if I was bothering him and dismissed me. I left the shop feeling guilty and upset. Coming from an older adult man you'd expect a little more maturity :/. I then went to the Brown's at Mirabel Premium Outlets and the sales associate there was so much more helpful and such a sweetheart.