3rd person gta like weapon problem??

I started making a game like gta a month ago. i made a simple every day movement: Idle-Walk-Run-Jump using mecanim

My question is how to add weapon using the mecanim "Humanoid".Itried using sub-state machine but it's noy doing the animation with the gun.like he is pretending to do.

Ps:I used unity "BotControllScript" and tweaked it.