It's super creepy hearing somebody's last words before a death they have absolutely no idea is coming. It obviously happened in a flash and those aboard probably only had seconds, if that, to realize what was happening.
At about 17:15 you can hear the tower trying to communicate with the plane. They ask another plane if they see anything about five miles off and they say nothing can be seen but I'd think the explosion would have been visible.
At about 20:00 they become aware that the plane probably crashed and at about 21:30 they declare an emergency.
At about 22:35 cactus 1452 reports they've been picking up on ice for awhile.
At about 23:58 they start talking to planes about icing. One plane says they have about a half inch of ice and the cactus 1452 states they've been having icing for about 10 minutes so far.
So it appears icing is a possible cause for the crash.
IIRC, Sully said cactus is the code word for a US Air flight.