Random.Range when instantiating things at start freezes the game

Hey i got an problem with instantiating prefabs (trees, rocks, bushes) on startup. I have a script to do it:

using UnityEngine;
using System.Collections;

public class raySpawn : MonoBehaviour {
public GameObject[] propy = new GameObject[30]; //Array of prefabs
private Vector3 origin;
private int index = 0;
private bool czyIndexPoprawny = false; //currently unused
	// Use this for initialization
	void Start () {
		origin = gameObject.transform.position;
		RaycastHit hit;
		for(int i = 0; i < 4000; i++)
		{
			Ray linia = new Ray(gameObject.transform.position, new Vector3(Random.Range(-1000,1000), -500, Random.Range(-1000,1000)));
			if(Physics.Raycast(linia,out hit) && hit.transform.tag == "ZaczepBudowy") //If it hits terrain
			{
				if(hit.point.y > 24) //So things wont generate at sea level
				{
					index = Random.Range(0,12);
					//if(index != null)
						Instantiate(propy[index],hit.point,Quaternion.identity);
				}
			}
			else
				i--;
			
			//Debug.Log(Random.Range(0,11).ToString()); I checked if its something horribly wrong with Random.Range itself
		}
	}
}

Theres currently 12 objects in array (0 to 11). I dont know why, but Random.Range(X,Y) includes the X but excludes the Y, so i have to add one digit to it. When i put 10 as a Y, it works (only 9 of 12 will spawn) but when i put 11 as Y, the game freezes horribly and makes F and S in FPS switch place. (Seconds per Frame ¯_(ツ)_/¯ ). I seek an solution for this. I checked if one prefab of those is causing a massive lag, but i found that not one of the prefabs is causing the problem.
Unaccounted takes up to 95% of memory in the profiler. I dont know why

The documentation says clearly, that Random.Range is max inclusive only for FLOATS.

Your solution to your infinite loop is to remove the following line, which causes the for loop counter to not increment:

else
  i--;