Delay with NavMeshAgent and Mecanim

So my goal is that the player should walk to a defined position and then stops and let the user have control of the player.

The problem I have is that if the player is in the distance of the objekt (1.0f) the agent is disabled but the animation still goes on for 3 seconds.

Anyone encountered the same problem?

This is my code I am using:

 void FixedUpdate () {
     if (goLeftSustain) {
         goToLeftSustain();
     }
 }

 void goToLeftSustain() {
     //Calculate distance between player and target object
     distanceLeft = Vector3.Distance(targetPlayerLeftSustain.position, fireFigher.position);
         
     //Define when player is in correct position to control left sustain
     if (distanceLeft < 1.0f) {
         stopLeft = true;
     }
         
     if (!stopLeft) {
         //Use Mecanim for walking animation
         animFirefighter.SetFloat(hash.speedForwardFloat, 1.0f, speedDampTime, Time.deltaTime);
         //Set Direction
         agent.destination = targetPlayerLeftSustain.position;
     } else {
         //Stop agent
         agent.Stop(true);
         //Stop Mecanim animation
         animFirefighter.SetFloat(hash.speedForwardFloat, 0, speedDampTime, Time.deltaTime);
         //Wait 4 secs for more realism then play animation
         //StartCoroutine(WaitForLeftSustainOut(1.0f));
         //goLeftSustain = false;

     }
 }

Edit:

So changing this line of Code does the trick:

  animFirefighter.SetFloat(hash.speedForwardFloat, 0, speedDampTime, Time.deltaTime);

to

  animFirefighter.SetFloat(hash.speedForwardFloat, -3.0f, speedDampTime, Time.deltaTime);

Can anyone explain it?