I just need help processing and dealing with this and I couldn't find anything like what I'm feeling by googling or searching this sub. 

So I was walking to my car after my class around 9pm (a night class that had run late). I saw a person in a reflective jacket who seemed to be holding something walking in the dark and approaching a classmate who was a few yards ahead of me getting on their bike. They rode away and he started walking without really any direction. When he noticed me, he began to walk in my direction. He asked me if I had a phone he could use, or if he could get into any campus buildings without a card. 

*All* the stranger danger criteria right there. 

And our campus has had some recent problems with randoms showing up and causing trouble. I pointed him in the direction of a building that is typically empty at 9pm but keeps the lights on, so that I would have time to get away (I was panicking). He told me he had been there and that everyone left him, and then told me he knows I have a phone. I was lucky that he eventually said thank you and kept walking away from me, and it should have been very relieving to me that I didn't get hurt. I recently got a notification from our campus safety patrol that they got the guy, and that should be even more relieving. 

But I can't stop thinking about it. I'm still freaked out about it, and I can't do anything at this point. Has anyone been in a similar situation unable to take your mind off of it? Any advice helps- I'm not sure I will be able to sleep.