After I paid and bought something, then the sales employee laughed extremely loud.

I went to Best Buy today and bought the Apple Care Warranty Service for the other $200 dollars device which I just also bought less than two days ago. First of all, that sales guy employee was upfront very rude attitude as I'm ACTUALLY PAYING HIM the money. Then, as soon as I paid money to him and we finished the transaction and after I asked that sales guy employee about a question regarding what is written on the warranty receipt about the warranty and as I walked away to leave the store, then out of no where, that sales guy employee laughed almost extremely loud, and I'm talking about he laughed not just very very loud, but he was laughing almost extremely loud. That happened after I finished paying the transaction and as I walked away to leave the store. I'm keeping my receipt to have an evidence that I bought something twice and this happened today in the store.