Ai instantly kills player [help]

Unity Engine
1

in my current script i have an ai that uses navmesh to avoid wallls and attacks the player when it gets near, my problem is i cant make it only attack once, so it instantly kills you when it gets near you.
any idea on how to stop this?

vartarget : Transform;
varisChasing : boolean = true;
varisAttacking : boolean = false;
varNavComponent : NavMeshAgent;
varthisObject : Transform;
varstopDistance : int;
varisInTeleporter : boolean = false;
varminSpeedWalk : int;
varmaxSpeedWalk : int;;
varminSpeedRun : int;
varmaxSpeedRun : int;
varminSpeedAttack : int;
varmaxSpeedAttack : int;
varisRunner : boolean;
varcurSpeed : int;
varmoveAnimName : String;
varwalkAnimName : String;
varrunAnimName : String;
varattackAnimName : String;
varidleAnimName : String;
vartimeToAttack : int;
varmaximumHitPoints = 5.0;

functionAwake(){
thisObject = transform;
}

functionStart(){
target = GameObject.FindWithTag("Player").transform;

NavComponent = thisObject.transform.GetComponent(NavMeshAgent);

if (isRunner){
curSpeed = Random.Range(minSpeedRun, maxSpeedRun);
moveAnimName = runAnimName;
 }

if (!isRunner){
curSpeed = Random.Range(minSpeedWalk, maxSpeedWalk);
moveAnimName = walkAnimName;
 }

NavComponent.speed = curSpeed;
}

functionUpdate(){

varcurDistance = Vector3.Distance(target.position, thisObject.position);

NavComponent.stoppingDistance = stopDistance;

if (curDistance <= stopDistance){
isChasing = false;
isAttacking = true;
 }

if (curDistance > stopDistance){
isChasing = true;
isAttacking = false;
 }

if (isChasing == true){
NavComponent.SetDestination(target.position);
NavComponent.Resume(); 
thisObject.animation.CrossFade(moveAnimName);
 }

if (isChasing == false){
NavComponent.Stop();
if (isAttacking == false){
thisObject.animation.CrossFade(idleAnimName);
 }
 }

if (isAttacking == true){ 
//target.SendMessage( "PlayerDamage"), maximumHitPoints);
//target.GetComponent("PlayerDamageNew").PlayerDamage("5");
thisObject.animation.CrossFade(attackAnimName);
waitFunction();
 }
}

functionwaitFunction(){
yieldWaitForSeconds (timeToAttack);
//target.GetComponent("PlayerDamageNew").PlayerDamage(5);
}

functionPlayerDamage(damage : float){
print ("PlayerReceives" + damage + "Damage!");
}
2

Cooldown between attacks?
Timer? Well in theory it should depend on weapon say if piston cd is like 0.25
if machinegun like 0.05 or something