Someone put semen in my hair today

I(16F)live in a big city in the US, and while sitting on the train coming back from school, a homeless person got on, and was asking people for money. I didn't have any so I said the truth. The man then asks everyone else in the train and comes to sit behind me. I had already had a gut suspicion about this guy but I decided to ignore it. After about few minutes I feel something touch my hair, and the man immediately gets up as I go to move it. I noticed though that his pants were not quite down to his knees but you could see the entirety of his underwear, and mind you his pants were fully up before he sat down. He said something to me but Icouldnt hear it, but he then left the train car. I reach back to feel if he put something in my hair and I felt something wet, I thought he just spit in my hair, but I turn around and see a white patch of goo on my hood. I thought it was snot at first but as I looked closer i realized it was semen. I'm currently locked out my house sobbing, waiting for my little brother to get home and let me in. I'm going to take the most in depth shower I have ever taken. I feel so violated. I don't know if I should report this because I don't know where this guy could possibly be but I can't comprehend how someone could do that to someone else