Many such instances had also been noticed in bangalore Rajdhani and shatabdi..
To tell yoy my personal experience, once was travelling in Golgumbaz Express from Kengeri, was at door step and enjoying the night beauty of city... suddenly big stone was pelted exactly in my door step... but due to moderate speed of train, it fortunately hit very near to my door in which I was standing.... such nuisance has created havoc....
They should either be based at WDP 4's smoke outlet or WAP's panto... just once and they will learn lesson