How to create “broken glass” animation?

I have started making a 3D game that consists in avoiding obstacles. It is very easy but I want to add a collision effect when I collide on the wall.

I would like to slice the screen into many parts (random pieces is better) that are falling down from screen with gravity.

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An example of what I mean:

ANIMATED GIF HERE: http://i.stack.imgur.com/L7JjD.gif

GIF PREVIEW:

How can I do this? I've tried using a lot of different images (shapes) but I'm sure that is not the best way...

Thanks for any suggestions.