What is the sequence of actions when my Shocker removes cards and places cards in my opponents hand?
When two or more trigger happen at the same time, the player controlling those triggers put them on the stack in an order of his/her choice, beginning with the active player.

So in your scenario, you can put the discard/draw trigger first and the bounce creature trigger second on the stack. This way, the bounce trigger will resolve first, so he/she will have to discard this creature, too, when the other trigger resolves.

Note, that he/she can respond to all triggers placed on the stack. If the bounced creature has Flash for example, he/she could replay it, before he/she has to discard