Score.cs

using UnityEngine;
using System.Collections;

/// <summary>
/// Attach this script to any object that modifies the score on its death
/// </summary>
public class Score : MonoBehaviour {

    public int score = 100;

    void OnDestroy()
    {
        GameObject.Find("Score").GetComponent<ScoreManager>().AddScore(score);
    }
}

ScoreManager.cs

using UnityEngine;
using System.Collections.Generic;
using UnityEngine.UI;

public class ScoreManager : MonoBehaviour {
    private int currScore;
    private List<int> scores;

	void Start () {
        scores = new List<int>();
	}
	
	void Update () {
	    if (scores.Count <= 0) return;
	    scores[0] -= 2;
	    currScore += 2;

	    if (scores[0] <= 0)
	    {
	        scores.RemoveAt(0);
	    }

	    // Update text display for the score
	    var textComponent = gameObject.GetComponent<Text>();
	    textComponent.text = currScore.ToString().PadLeft(8, '0');
	}

    public void AddScore(int score)
    {
        scores.Add(score);
    }
}