[Zombie AI] Enemy grows and pushes me when coming towards me?

Hello everyone! I've recently taken to creating a zombie game and I've found some code online to help me get started with the AI of the creatures. It works fairly well, but not perfectly. You see, when I get in range of the zombie, it turns and moves towards me (like it should) but slowly grows in size and seems to push my actual player backwards as it does so.

I'm not entirely sure, but I think it may be how I'm playing the animations in the scene?

 var target : Transform; //the enemy's target
 
 var moveSpeed = 3; //move speed
 
 var rotationSpeed = 3; //speed of turning
 
 var attackThreshold = 1.5; // distance within which to attack
 
 var chaseThreshold = 10; // distance within which to start chasing
 
 var giveUpThreshold = 20; // distance beyond which AI gives up
 
 var attackRepeatTime = 1; // delay between attacks when within range
 
 
 
 private var chasing = false;
 
 public var attackTime : float;
 
 
 
 var myTransform : Transform; //current transform data of this enemy
 
 
 
 function Awake()
 
 {
 
     myTransform = transform; //cache transform data for easy access/preformance 
 
     }
 
 
 
 
 
 function Start()
 
 {
 
      if (target == null && GameObject.FindWithTag("Player"))
 
         target = GameObject.FindWithTag("Player").transform;
 
 }
 
 
 
 function Update () {
 
 
 
     // check distance to target every frame:
 
     var distance = (target.position - myTransform.position).magnitude;
 
 
 
     if (chasing) {
 
 
 
         //rotate to look at the player
 
         myTransform.rotation = Quaternion.Slerp(myTransform.rotation,
 
         Quaternion.LookRotation(target.position - myTransform.position), rotationSpeed*Time.deltaTime);
 
 
 
         //move towards the player
 
         myTransform.position += myTransform.forward * moveSpeed * Time.deltaTime;
 
 
 
         animation.Play("run");
 
 
 
         // give up, if too far away from target:
 
         if (distance > giveUpThreshold) {
 
             chasing = false;
 
         }
 
 
 
         // attack, if close enough, and if time is OK:
 
         if (distance < attackThreshold && Time.time > attackRepeatTime) {
 
                     animation.Play("attack");
 
                     target.SendMessage("ApplyDamage",10);
 
             // Attack! (call whatever attack function you like here)
 
             }
 
         if (distance < attackThreshold) {
 
         moveSpeed=0;
 
         //stop when close enough
 
     }
 
 
 
             attackTime = Time.time+ attackRepeatTime;
 
         }
 
 
 
       else {
 
         // not currently chasing.
 
         animation.Play("idle");
 
         // start chasing if target comes close enough
 
         if (distance < chaseThreshold) {
 
             chasing = true;
 
         }
 
     }
 }
 
 function OnTriggerEnter (other: Collider) {
 
 if (other.gameObject.CompareTag("Bullet")){
 
 chaseThreshold=100000000;
 
 }
 
 }

 

Thanks for your help!

EDIT: Sorry for the odd editing, I'm not quite sure what I've done. Hopefully you can still read it.