AI cannot find closest Target

Hello Everyone, I have a fox that attacks humans when they are too close, but the problem is, it will only attack the one gameobject I assign it too. I want the game to be multiplayer, so I want it to attack anything with the tag "Player" when it gets too close. The script I made seems to have problems assigning the closest target. Could anyone explain to me what I am doing wrong. I greatly appreciate your help.

Here is my script.

 var Target : Transform;
 var Distance;
 
 var LookatDistance = 25.0;
 var ChaseRange = 15.0;
 var AttackRange = 2.0;
 var MoveSpeed = 5.0;
 var Damping = 6.0;
 var AttackRepeatTime = 1;
 
 
 var moveSpeedCalm = 0.2;
 var ChaseRangeCalm = 0.5;
 var LookatDistanceCalm = 0.7;
 
 var isAngry: foxWalkScript;
 
 var MonsterAttack = 25;
 
 private var AttackTime : float;
 
 var controller : CharacterController;
 var Gravity  : float = 20.0;
 private var MoveDirection : Vector3 = Vector3.zero;
 
 
 
 
 function Start ()
 {
 
     AttackTime = Time.time;
     
     
 }
 
 function Update ()
 
 {
     
         Distance = Vector3.Distance(Target.position, transform.position);
         
         if (Distance > LookatDistance)
         {
 
             isAngry.provoked =false;
         }
         if (Distance < LookatDistance)
         {
 
             LookAt();
         }
         
         
         if (Distance < AttackRange)
         {
             Attack ();
             isAngry.provoked =true;
         }
          
         else if (Distance < ChaseRange) 
         {
             chase ();
             isAngry.provoked =true;
         }
         
         
                    //////////////////
              var direction = transform.TransformDirection(Vector3.forward);
             var hit : RaycastHit;
  
            if (Physics.Raycast (transform.position, direction, hit, 20)) 
                {
            Debug.DrawLine (transform.position, hit.point, Color.yellow);
             }
             /////////////////        
     
 }
 
 
 function LookAt ()
 {
 
     Target =  GameObject.FindGameObjectWithTag("player").transform;
     yield WaitForSeconds(0.1);
     var rotation = Quaternion.LookRotation(Target.position - transform.position);
     transform.rotation = Quaternion.Slerp(transform.rotation, rotation, Time.deltaTime * Damping);
 }
 
 function chase ()
 {
 
     moveDirection = transform.forward;
     moveDirection *= MoveSpeed;
     
     moveDirection.y -= Gravity * Time.deltaTime;
     controller.Move(moveDirection * Time.deltaTime);
      
 }
 
 function Attack ()
 {
     if (Time.time > AttackTime)
     {
         Target.SendMessage("ApplyDamage", MonsterAttack );
         Debug.Log ("Insert Attack Here");
         AttackTime = Time.time + AttackRepeatTime;
     }
     
 }
 
 function ApplyDamage ()
 {
 if (isAngry.provoked == true)
     {
     ChaseRange = 4;
     MoveSpeed = 2;
     LookatDistance = 4;
     }
 }
 
 

Its suppose to assign the target at the LookAt function, but doesn't want to...