There are Three Layers.
Outer & Inner are the Load Bearing ones.The Inboard most is an Acrylic layer & can be cracked.No big deal.
The Question was Why did it occur.Was it Intentional.
regds
MEL
Yes, its easy to break the inner window.
In an old and grounded NEPC Airlines F27 in Chennai, aircraft engineers once showed how its quite easy to just smash through with a bare hand.
This is my experience...
When at Nepal i flew RNAC between pokhra and kathmandu, the Cessna Twin Otter we flew didnt have windows on the co-pilot side!
The a/c flies at generally 6,000-7,000 ft above the GROUND