I was in HS. At the time it was a big deal because we were just a year past the Cuban missile crisis, and JFK got us through that, just fine. Very sad to see his wife and children. Sadly that was followed by similar killings of MLK & RFK. Also saw Oswald shot, on live TV. Remember hearing that it was the first live televised murder.
Horrific events such as that, the Challenger explosion etc. do stay with you, but now 56 years later, the day is barely mentioned. We only had :15-30 minute evening network TV news then but this took up almost 4 days of continuous TV.
The AFL (Buffalo) didn't play that Sunday but the NFL did. It was the right call for the AFL to make.