Ok I'll spill. It was indeed the fire alarm.
I heard "CODE RED! CODE RED! Connell 5" coming over the PA. I looked at my wife. "I know we are on the 5th floor. Not sure about the wing?" She assured me it was Connell all right. Ugh.
I peaked out the door. Nurses and orderlies were rushing past. Then the firefighters arrived in full gear. They initially trudged past us and went into other rooms, but then they turned around and made a B-line for us. They barged in and knocked around the place. Spent a lot longer with us than anywhere else. Then one of them noticed I was holding a camera. "Could I see that?"
He took the thing apart and eventually pronounced "Yep, this is our culprit right here. The flash set off the detector." I just remember feeling smaller and smaller and wishing I could disappear into the floor.