Something happened yesterday.

There had been a no smoking policy on our campus since Jan 2014. I have had to inform many students of this and ask them to put out their cigarettes and they have always complied right away. 
But yesterday was different. I had just finished class and was walking back when I noticed a student who was walking the opposite direction had a lit cigarette. I approached him and informed him about the smoke-free policy and asked him to put it out. He responded saying that he would and continued walking.
Now, I usually watch a person until the put it out (which they do because they don't really want me to stand there until they finish smoking) but this guy was walking and he didn't put it out even after he walked off. So I silently followed him. This pursuit went something like this:
"Are you following me?"
"Yeah, I'm just making sure you put it out and then I'll leave"
"Well where do you want me to put it out? There's no where to do it"
"You can snub it out on the ground and then throw it in the trash can"
"Okay, whatever, you can follow me to lot 30 where I parked my car"
...
"Can you stop f*ing following me?"
"I will as soon as you put it out"
"You're f*ing crazy you know?"
"Thank you"
"Can you just go away?"
"I will as soon as you put it out. It's a very simple request"
"Well my request is simpler, just stop f*ing following me"

This happened the entire walk across campus. He took out his phone to snap a picture/video of me before he threw it onto the grass next to the bus stop. I had to go step on it and pick it up to throw it into the trash can.
I also informed him some time throughout this interaction that he can light another one as soon as he gets off campus.

Three things upset me: he didn't put it out right away, he felt the need to curse at me even though I didn't curse back, and that he took a picture of me that might end up online somewhere.

I'd really like some feedback on this. What do you guys think? What should I have done? What would you have done?
And do not say to leave it alone because if one person gets away with it, they all get away with it. Next time he thinks about lighting up on campus, he'll probably get a flashback of that crazy girl that followed him all the way across campus.
(And I think I might have a little PTSD because I started to feel a little panicked when I passed that spot on the grass where I saw him yesterday. Not a good feeling.)