Mecanim animator layers

I have 2 layers, the first layer is for all the basic movement animations (walk, run, jump, idle) and the second overrides the upperbody for things like blocking and hand gestures. My problem is: im trying to do blocking, i have 2 animations. the first is block start and the second is block idle. They are transitioned on a bool "blocking".

 if (Input.GetMouseButton (1)) {
                     if (!blocking) {
                         blocking = true;
                         animator.SetLayerWeight (1, 1);
                         animator.SetBool ("blocking", true);
                     }
                 } else if (!Input.GetMouseButton (1)) {
                     if (blocking) {
                         blocking = false;
                         animator.SetBool ("blocking", false);
                         animator.SetLayerWeight (1, 0);
                     }
                 }

The first time i hold the block button the "block start" animation is fired and transitions to the "block idle", then it loops until i release the button. The problem is when i press the block button after, it starts off at the "block idle". I want it to start off with "block start" again.