AITA for making a dad joke in an inappropriate situation

I (25m) was at my girlfriends (25f) family reunion. I got aquainted with her family on the first day of the reunion and on the second day I had to attend her grandmothers funeral. She was ill for a while and passed away the morning before.<br><br>Her family was very friendly to me and I wanted to show that I care for them and started telling jokes during dinner to lift up the mood. I told a few and they all laughed and seemed to enjoy them. I was about to go to bed when I made my last joke of the night to her uncle<br><br>(who is a retired army first sergeant that loves veteran and army related jokes) saying “why did grand ma cross the road? Because she finally found a way to get to the other side!”<br><br>He didn’t laugh but looked very stern instead. The next day her dad and uncle ran into me at the local store and said I should not have made that joke at that time. I said sorry and explained that I didn’t mean to offend. Her dad then told me that she is very religious and that the uncle is no longer as heavy on jokes. I apologised again and offered to drive them to the airport two days later free of charge as they didn’t have a driver on the return day. They didn’t talk to me and told me I have to go back home the day before.<br><br>My girlfriend called me later on and told me she is mad at me for the joke. I explained that it was not my intent to hurt their feelings and that I only wanted to lighten up the mood. She hung up on me. I haven’t heard from her since and I don’t know what to do.