When my charity attempt BACKFIRED!

So it all began in the wal-mart parking lot. Low and behold as I drove past the wal mart parking lot, a skinny, little, old, dirty, sad lookin man stood holding a cardboard sign that merely said "PLEASE HELP ME." Needless to say I knew that if I did not do something for him I would not be able to stop thinking about what I could have done for him. So I decided to buy him some food. I hurried about...well as fast as you can in wal-mart...and left the store complete with enough groceries for the sidewalk stander to last a couple of days. As I was unloading my groceries, I noticed a woman standing behind me. I turned around to see a women who was probably in her mid forties. It didn't take me long to realize that she wasn't all there, or as some may say she was a few cards short of a full deck.. or maybe missing about half. She asked if she could get a ride to the other side of town. She then began ranting about something and everything. I tried to see if there was anyone I could call for her. This began another rant filled answer. The entire time I was trying to figure out what I should do. I knew that I wanted to help her, but I also knew it could be a potentially scarry situation. After about five minutes, I told her I was so sorry but I was on my to class and couldn't take her home. I got in my car still asking myself if I had made the right desicion. It gets worse, by the time I got back to where the man was...he was gone. I made a couple loops but could not find him. So while trying to help someone out, I ended up turning someone away, not helping the man, and feeling worse than if I would have kept driving. That's about my luck I guess. Did I do the right thing, should I have taken the "crazy" lady home? I don't know, what do ya'll think?