Copying the value of instant of other instant variable with Random.Range make unexpected behavior?

I make a simple script for testing...
I attach a zip file...
The bulletPattern.respawnOffset changes over time even it's for patternApply.respawnOffset, I mean I don't even initialize the bulletPattern.respawnOffset, but it changes. It's hard to explain, just see and test the script...
I want to know why this happen?

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. [System.Serializable]
5. public class TransformPattern {
6.     public GameObject bulletPrefab;
7.     [Header("Bullet Patterns:")]
8.     public Vector2 respawnOffset;
9.     public Vector2 masterOffset;
10.     public string stringVar;
11.     //if I have more List with List...
12. }
13.  
14. public class RandomRespawnTest : MonoBehaviour {
15.     [Header("Bullet Transform:")]
16.     public TransformPattern bulletPattern = new TransformPattern();
17.     void Update () {
18.         startRespawn ();
19.     }
20.  
21.     void startRespawn ()
22.     {
23.         TransformPattern patternApply = new TransformPattern();
24.         /*
25.             //Imagine, if I have many variable in TransformPattern... Instead of doing this, individually:
26.                 patternApply.masterOffset = bulletPattern.masterOffset;
27.                 patternApply.stringVar = bulletPattern.stringVar;
28.                 patternApply.otherVar_1 = bulletPattern.otherVar_1;
29.                 patternApply.otherVar_2 = bulletPattern.otherVar_2;
30.                 patternApply.otherVar_3 = bulletPattern.otherVar_3;
31.             I do below, and successfully copy everything, but there's a problem:
32.         */
33.    
34.         /* Take one of these three line by commenting other two out by // to see results */
35.  
36.             //patternApply.masterOffset = bulletPattern.masterOffset;
37.             //patternApply.masterOffset = bulletPattern.masterOffset; patternApply.stringVar = bulletPattern.stringVar;
38.             patternApply = bulletPattern; /* Initialize patternApply... Problem manifest here... why? It's weird? Why the bulletPattern manipulated? Even nothing touches it or I initialize it? 'patternApply' and 'bulletPattern' are two different variables, right? */
39.  
40.         /* ^ Swap these three to see results: */
41.  
42.         if(patternApply.stringVar == null || patternApply.stringVar == "")
43.             patternApply.stringVar = "Other Variable, SEE?";
44.    
45.         //Get the random generated value range from bulletPattern.respawnOffset for patternApply.respawnOffset...
46.         float respawnOffsetX = Random.Range (-bulletPattern.respawnOffset.x, bulletPattern.respawnOffset.x);
47.         float respawnOffsetY = Random.Range (-bulletPattern.respawnOffset.y, bulletPattern.respawnOffset.y);
48.         Debug.Log ("bulletPattern.stringVar: "+bulletPattern.stringVar+" | patternApply.stringVar: "+patternApply.stringVar);
49.  
50.         patternApply.respawnOffset = new Vector2 (respawnOffsetX, respawnOffsetY);
51.  
52.         Vector3 respawnOffset_V3 = new Vector3 (patternApply.respawnOffset.x, patternApply.respawnOffset.y, 0f);
53.         Vector3 masterOffset_V3 = new Vector3 (patternApply.masterOffset.x, patternApply.masterOffset.y, 0f);
54.         Vector3 transformPosition = transform.position + respawnOffset_V3 + masterOffset_V3;
55.         //Debug.Log (transformPosition);
56.  
57.         Instantiate (patternApply.bulletPrefab, transformPosition, transform.rotation);
58.     }
59. }

This is my real script I'm working on, this is kind of pain if I initialize all (some) of this:
(Disregard this, for illustration purpose only)

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3. using System.Collections.Generic;
4.  
5. [System.Serializable]
6. public class BulletModification {
7.     [Header("Modify Cluster:")]
8.     public float startSpeed;
9.     public enum generateAcceleration {
10.         byUnit,
11.         byPercentage
12.     } public generateAcceleration accelerationType;
13.     public float acceleration;
14.     public float speedRange;
15. }
16.  
17. [System.Serializable]
18. public class TransformFormula {
19.     //[Header("Stir Bullet:")]
20.     [Header("Mirror Bullet:")]
21.     [Tooltip("0 means all copies will be on sync, beyond that will make delay offset speed; 100 makes the last delay copy to stationary, 200 makes go to opposite direction. Set delayAmount above 0 to see result")]
22.     [Range(0,200)] public float speedOffset;
23.     [Tooltip("Number of clone bullets for offset speed. Set speedOffset to work with")]
24.     [Range(0,3)] public int delayAmount;
25.     [Tooltip("Number of clone bullets shoot parallel to each other")]
26.     [Range(1,128)] public int linearAmount = 1;
27.     public enum spaceType {
28.         byUnitAway,
29.         byOverallWidth
30.     }; [Tooltip("How parallel bullets take up space")] public spaceType areaOccupy;
31.     [Tooltip("The amount of parallel bullets away each other or their general width as one group")]
32.     public float spacingValue;
33.     [Tooltip("Number in seconds; parallel from the middle will start immediately, then delay start to the next neighbor line")]
34.     [Range(0,20)] public float delayLinear;
35.  
36.     [Header("Spray Bullet:")]
37.     [Tooltip("The degree angle of an arc be made for rayAmount")]
38.     [Range(0,360)] public float spreadAngle;
39.     [Tooltip("The number of copy bullet as rays restricted by spreadAngle")]
40.     [Range(1,32)] public int rayAmount = 1;
41.     [Tooltip("The radius offset of the center of the ray")]
42.     public float spawnOffsetRadius;
43.     [Tooltip("Number in seconds; the first ray will start immediately, then delay start to the next neighbor ray")]
44.     [Range(0,20)] public float delayRay;
45. }
46.  
47. [System.Serializable]
48. public class TransformPattern {
49.     [Header("Bullet Patterns:")]
50.     public Vector2 respawnOffset;
51.     [Tooltip("Sliding the respawn origin of bullet sideward from left to right length-based over given duration")]
52.     public float linearMagnitude;
53.     public enum linearMotionType{
54.         Linear,
55.         Wave
56.     }; public linearMotionType linearFlow;
57.     public enum linearDirection{
58.         left_Right,
59.         right_Left,
60.         center_Right,
61.         center_Left
62.     }; public linearDirection linearPoint;
63.     [Tooltip("Move with one direction or play ping pong")]
64.     public bool pingPong = true;
65.     [Tooltip("The spin progress over given duration; Note: clinch with 'Linear Magnitude'")]
66.     public float spinMotion;
67.     public enum spinMotionType {
68.         Linear,
69.         Wave
70.     }; public spinMotionType spinFlow;
71.     public enum spinDirection{
72.         left_Right,
73.         right_Left,
74.         center_Right,
75.         center_Left
76.     }; public spinDirection spinPoint;
77.     [Tooltip("Merry-go-around or not")]
78.     public bool swingBack = false;
79.     [Tooltip("As it says; offset vertically and/or horizontally -_-")]
80.     public Vector2 masterOffset;
81.     [Tooltip("Offset overall rotation with parent object, but only in z-axis, any problem with that?! Note: doesn't spin over time, use spinMotion or bullet formula instead, or use emitter and make it spin via other script (or animation?)")]
82.     public float masterRotation;
83.     [Tooltip("Offset rotation disregarding linear orientation")]
84.     public float offsetRotation;
85. }
86.  
87. [System.Serializable]
88. public class TimeLine {
89.     [Header("Bullet Time:")]
90.     [Tooltip("Ready to execute one time once timeCode reaches")]
91.     public bool active = true;
92.     [Tooltip("Time in seconds to start the bullet party")]
93.     public float start;
94.     [Tooltip("Time in seconds to finish one pattern")]
95.     public float duration;
96.     [Tooltip("One more duration to repeat the pattern")]
97.     public int repeat;
98.     [Tooltip("Number of bullet emits in one span of duration harmonizing with pattern; Note: minimum fire rate will not less than 0.1 sec, or else actionPulse will be deducted")]
99.     public int actionPulse;
100.  
101.     [Header("Bullet Element:")]
102.     [Tooltip("To certainly choose none, input less than 0")]
103.     public int pattern;
104.     [Tooltip("To certainly choose none, input less than 0")]
105.     public int formula;
106.     [Tooltip("To certainly choose none, input less than 0")]
107.     public int modification;
108. }
109.  
110. [System.Serializable]
111. public class BulletSpawn {
112.     [Tooltip("Your title, definition, description, speech, message, or whatever; :Optional:")]
113.     public string name;
114.     public GameObject bulletPrefab;
115.     [Tooltip("Spawn point: object attached with this script act as default emitter, if leave empty")]
116.     public List<GameObject> emitter;
117.     public List<TimeLine> bulletTime;
118. }
119.  
120. [System.Serializable]
121. public class Bulletflow {
122.     /* Note: for the future viewer; why no 'public bool active'?
123.      * No need, I found it useless; use/code timeHalt + reset = inactive (if you want to extend this code)... */
124.     public bool reset;
125.     public bool timeHalt;
126.     public bool looping;
127.     [Tooltip("Set loopQuantity to zero for infinite loop")]
128.     public int loopQuantity;
129.     [Tooltip("What for? Delay the start time of timeCode")]
130.     public float delayStart;
131.     [Tooltip("Behold the time holder! NOLI ME TANGERE, if you don't know me what I am for")]
132.     public float timeCode;
133. }
134.  
135. public class HellBulletManager_New : MonoBehaviour {
136.  
137.     [Header("Bullet Manager:")]
138.     public Bulletflow bulletRush;
139.     public List<BulletSpawn> hellBullets;
140.  
141.     [Header("Bullet Transform:")]
142.     public List<TransformPattern> bulletPattern = new List<TransformPattern> ();
143.  
144.     [Header("Bullet Properties:")]
145.     public List<TransformFormula> bulletFormula;
146.     public List<BulletModification> bulletModification;
147. }