Ok I AM A BANK TELLER...
I am guessing it is different bank policy in US but here in canada you are told to take the note read the note and if it IS a robbery note, aka usual is "give me all your money in your till, don't say a word, etc". My bank has been robbed twice while I've been working and standard procedure is take the note give the robber the money in the till and the dye pack (bait money) as soon as the robber leaves through the door the dye pack is activated and it's only a matter of time before he or she is caught. This procedure helps the robber keep his cool because he thinks he is in control and this causes the least amount of violence.
We've never had a violent robber and this is very rare as well. I think the button is somewhat ridiculous as there is SO much that can happen in between that button being pressed and when the cops come and this can usually result in violence or a hostage situation. But again that doesn't happen much either anymore...the robbers top priority is to get in and get out they don't wanna stick around cuz 9 times out of 10 they are most scared than you are and are just stupid for doing what they're doing.
After the robber leaves there is a procedure booklet in which to proceed with and this is when the cops come and you tell your supervisor, manager.