Yeah, you seem to hear more and more about these subway incidents!
My story is also O/T ish but last night I had my first encounter like that, and I'll never forget the lady who helped me, and reminded me about the importance of kind/vigilant strangers in the face of evil like this. I dozed off on my usual Brooklyn bound train after leaving a bar after work and I woke up to a woman sitting next to me and asking if I was getting off soon, because the guy across from us, she said, had been harassing her for several stops and being lewd and touching himself. Apparently he set his sights on me when he noticed I was falling asleep, and she came over to wake me and tell me about him. As she was doing this he stared cursing at us, touching himself more, generally being weird - I did wake up at one point and notice him but figured he was just a drunk person. I pretended that I had many many stops to go (she winked at me and played along) and then I basically ran out of the train mid-sentence when it was actually my stop. I was so, so grateful for her and yes, worried about leaving her there - I called the transit police right away to report it and they said they would try to have someone there by one of the upcoming platforms for that train.
She was also watching forensic files on a laptop and called herself a true crime buff, which makes her alert to weird/creepy behavior like this - hah, if that was one of you sleuths in person, thank you so much!

And yes, I was chastised by the person I had been with in the city earlier, who was already worried about the late subway ride and asking me to text when I get home. I'll be careful about falling asleep from now on.