What if the timer hit the horn because he was tased by the shot clock operator?

stupid..lol..don't tase me bro!

We don't know the intentions of the shot clock operator.

Let's make this easy. If the horn sounds... blow your whistle and kill the whole thing immediately.... before the shot attempt begins. Then figure out what is going on at the table, take care of the 5th foul then readminister the free throw. By waiting and the player missing the free throw you open a can of worms that we don't want/need to address. Squish the lizard before it turns into a dragon!

What if the horn doesn't sound before the attempt begins (which is how I read the OP)? ;)

I would still blow my whistle as loud as possible in the timer's ear. :)