I was an Army Captain working at an Air Force radar squadron at Cape Charles VA. We were running an air defense exercise in the operations room. One of the plotters (writes backwards on the plexiglas chart) had a headset on, and had contact with Ft Lee, VA. He suddenly said, real loud, "The President's been shot!". We really didn' believe it, but soon after we got 'fadeout' (end of exercise) and the official announcement from higher headquarters.
One of the officers was having a party that night. The party was cancelled, but we all went over there and watched TV. It was terribly gloomy.
I think we went up a notch on DEFCON for a couple of days, too, and nobody could leave the base.