Why would my arrow of light(old) randomly fall?

I was just trying to sleep then boom! Bang loud noises and **** happen! In like what the ****!!! Ran diff out of bed and turn on the light scared as he'll. But before it happend I noticed my cat kindof staring in it's direction of the room.. It was hung up by thumb tacks which are strong. Can anyone tell me what has happend? I know it sound weird..