It could have possibly been used for target practice, but, I just think it's because it's been left unnattended since 1926, when it was discontinued. I read somewhere that there are plans for it's restoration, but, it seems unlikely.
Here are a few other pictures I located of the lighthouse
Port Ferro with it\'s Lantern Room
Port Ferro without it\'s lantern room before it was sealed off
Lighthouse People pics where you can see the modern light
Also, Bert, there are infact 2 lighthouses at Vieques. Port Ferro, which you can visit by obtaining a visitor's pass to get into the USMC Base and Point Mulas Which is in way better shape than Port Ferro and open to the public for climbing.