Checking the distance between an instantiated object and an existing object

Hi there! In my game, if a person is struck by lightning, then they die. The lightning spawns wherever the user clicks, and I don’t know how to check to see if the lighting bolt(which is instantiated) spawns near enough the person. The lightning bolt spawns at the x and z point of the click, and the y point has 100 added to it.

Here is my script to far (I know I misspelt the lightning variable):

var lightingBolt : GameObject;
var hit : RaycastHit;
var person : GameObject;
var distance = Vector3.Distance(lightingBolt.transform.position, person.transform.position);

function Update () {
if (Input.GetButtonDown ("Fire1")) {
var ray = Camera.main.ScreenPointToRay (Input.mousePosition);
if (Physics.Raycast (ray, hit)) {
hit.point.y = hit.point.y + 100;
Instantiate (lightingBolt, hit.point, transform.rotation);

Instantiate() returns the instantiated object, so you can get its transform and then use that to find the distance:

var bolt = (GameObject)Instantiate(lightingBolt, 
    hit.point, transform.rotation);
float distance = Vector3.Distance(bolt.transform.position, 
if (distance < 10f) {
    // do your thing

Obviously change 10f to whatever distance you want to check for, but this should work otherwise.