unity editor freezes on play, because of script

hey everyone,

I'm on Unity 5.5.2f1. i tried to make an enemy AI using navMeshAgent and a Finite State Machine. the script is below.

now when I added that script to my enemy and pressed play, the editor froze, and I can't get out of unity unless I go to task manager and kill it.

i'm pretty certain it's this script because when i remove it and add my other ai script, everything runs fine. I'm fairly new to scripting in general, and even though i know i'm missing something in the script, i can't find out what.

kind regards,

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.AI;
 
 public class StateMachineAI : MonoBehaviour {
 
     public NavMeshAgent agent;
 
     public enum State
     {
         PATROL,
         CHASE,
         SHOOT,
         RUN
     }
 
     public State state;
     private bool alive;
 
 
 
 
     //vars for patrolling
     public GameObject[] waypoints;
     private int waypointIndex;
     public float patrolSpeed = .5f;
 
     //vars for chasing
     public float chaseSpeed = 1f;
     private float targetDistance;
     public GameObject target;
 
     //vars for seeing
     public float sightDist = 10f;
     public float heightMultiplier = 1.35f;
     public bool targetFound;
 
 
     //vars for running
     public float runSpeed = .7f;
 
     //vars for shooting
     public bool shooting;
     public Transform player;
     
     
 
 
     
     void Start () {
 
         agent = GetComponent<NavMeshAgent>();
         agent.updatePosition = true;
         agent.updateRotation = true;
 
         waypoints = GameObject.FindGameObjectsWithTag("waypoint");
         waypointIndex = Random.Range(0, waypoints.Length);
 
         alive = true;
         shooting = false;
         targetFound = false;
 
         state = StateMachineAI.State.PATROL;
     }
     
     
     void Update () {
         StartCoroutine("FSM");
         if (targetFound)
         {
             if (Vector3.Distance(target.transform.position, transform.position) >= GetComponentInChildren<RayGun>().weaponRange && GetComponent<enemyHealth>().curHealth > 20)
             {
                 state = StateMachineAI.State.CHASE;
             }
             if (Vector3.Distance(target.transform.position, transform.position) <= GetComponentInChildren<RayGun>().weaponRange && GetComponent<enemyHealth>().curHealth > 20)
             {
                 state = StateMachineAI.State.SHOOT;
             }
             if (GetComponent<enemyHealth>().curHealth <= 20)
             {
                 state = StateMachineAI.State.RUN;
             }
             else
             {
                 state = StateMachineAI.State.PATROL;
             }
         }
     }
 
     IEnumerator FSM()
     {
         while(alive)
             switch (state)
             {
                 case State.PATROL:
                     Patrol();
                     break;
 
                 case State.CHASE:
                     Chase();
                     break;
 
                 case State.SHOOT:
                     Shoot();
                     break;
 
                 case State.RUN:
                     Run();
                     break;
             }
 
         yield return null;
     }
 
     void Patrol()
     {
         agent.speed = patrolSpeed;
         if (Vector3.Distance(this.transform.position, waypoints[waypointIndex].transform.position) >= 2)
         {
             agent.SetDestination(waypoints[waypointIndex].transform.position);
         }
         else if (Vector3.Distance(this.transform.position, waypoints[waypointIndex].transform.position) <= 2)
         {
             waypointIndex = Random.Range(0, waypoints.Length);
         }
         //else
        // {
             //should be a still animation, dunno what to do with this
        // }
     }
 
     void Chase()
     {
         agent.speed = chaseSpeed;
         agent.SetDestination(target.transform.position);
     }
 
     void Shoot()
     {
         //something to initiate the raygun script when target is spotted
         shooting = true;
         
         
     }
 
     void Run()
     {
         agent.speed = runSpeed;
         agent.SetDestination(waypoints[waypointIndex].transform.position);
         shooting = false;
     }
 
     private void FixedUpdate() //sighting raycast function
     {
         RaycastHit hit;
         Debug.DrawRay(transform.position + Vector3.up * heightMultiplier, transform.forward * sightDist, Color.green);
         Debug.DrawRay(transform.position + Vector3.up * heightMultiplier, (transform.forward + transform.right).normalized * sightDist, Color.green);
         Debug.DrawRay(transform.position + Vector3.up * heightMultiplier, (transform.forward - transform.right).normalized * sightDist, Color.green);
 
         if (Physics.Raycast(transform.position + Vector3.up * heightMultiplier, transform.forward, out hit, sightDist))
         {
             if (hit.collider.gameObject.tag == "Player")
             {
                 targetFound = true;
                 //state = StateMachineAI.State.CHASE;
                 target = hit.collider.gameObject;
             }
         }
 
         if (Physics.Raycast(transform.position + Vector3.up * heightMultiplier, (transform.forward + transform.right).normalized, out hit, sightDist))
         {
             if (hit.collider.gameObject.tag == "Player")
             {
                 targetFound = true;
                 //state = StateMachineAI.State.CHASE;
                 target = hit.collider.gameObject;
             }
         }
 
         if (Physics.Raycast(transform.position + Vector3.up * heightMultiplier, (transform.forward - transform.right).normalized, out hit, sightDist))
         {
             if (hit.collider.gameObject.tag == "Player")
             {
                 targetFound = true;
                 //state = StateMachineAI.State.CHASE;
                 target = hit.collider.gameObject;
             }
         }
     }
 }