i think we can get kind of distracted with our head phones on and we don't realize what's going on around us. this was a gentleman standing in the bulk head talking to the flight attendants and i went up. i was sitting in row five. i went to go to the bathroom. he was standing there and said the bathroom is closed. that seemed strange to me but i didn't think much of it. i went to the back. when i sat down in my seat, there was an offduty pilot next to me and he was really concerned with what was happening up front. and the gentleman was wearing a bicycle helmet and a hoodie. i wasn't thinking much of it but this gentleman was expressing concern. he said he wanted to go up and see what's going on. i would help him and be his back-up. this gentleman got on the intercom and started talking about oxygen masks and prepare for putting on your oxygen mask.