Why was he mad at me? I didn't do anything?

this man in JC Penny's saw me going into the store (I was between the two sets of doors in my wheelchair) and he yelled from the shoe section (which isn't very close to the door) "I'll get that for you" and he ran all the way to the door to open it for me even though I didn't have any problem with the other door and I was about to open the second door. and I was very embarred so I smiled and said "thank you but I could have gotten that myself" (and I didn't say it rudely at all because I knew he was just trying to help.) and when I was leaving the store he was still there and I got both doors myself, but before I left he was glaring at me while I went past the shoe section.