Unintentional Stalker

The other day I was walking to the local Rite-Aid to get deodorant and soap. My path takes me across Colorado Avenue, right at Lake Avenue, one of the busiest intersections in Pasadena. Since my day is essentially my own now, I was running this errand smack in the middle of the afternoon, past the lunch hour but before quitting time. The streets were still busy, but there weren't quite as many pedestrians, and the traffic wasn't dangerously heavy. I was minding my own business, just doing my thing, when I saw him.
   A little over five feet tall, a gnome of a man stood near a bus stop, tapping a newspaper dispenser and muttering under his breath. He had a grizzled, long beard, like a salt-and-pepper Santa Claus, an Australian-style hat on his head, a tweed jacket, olive cargo pants with obviously full pockets, and worn tennis shoes. His eyes were covered by dark sunglasses and on his back he carried an enormous knapsack, full to bursting.
   He was either one of the local homeless people or professor at nearby CalTech, I couldn't decide which. He wasn't one of the homeless people I knew - since I walked to work I'm familiar with many of them - but he didn't look... sane enough to be a professor at CalTech (I know, that sounds odd to me too).
   As I approached he started walking towards me, still muttering. Then he stopped, turned around, and started walking the way I was going. I noticed a thing in one of the outside pockets of his backpack, it looked like a one of those folding canes that blind people use, but this wasn't white, it was all red. I decided to follow, to see if I could classify him definitively.
   The odd man would walk very purposefully for half a block, outpacing me on his stumpy legs, then he'd stop, put his hand to his chin and mutter. The backpack looked very heavy and the closer I got the more I could see how worn and dirty his clothes were. I was leaning towards a 'homeless' classification, but none of the regulars in my neighborhood wear backpacks, especially not heavy ones with odd folded red things in their pockets. Shopping carts are the preferred baggage here. So the 'CalTech professor' classification seemed valid.
   This continued for several blocks, this guy going the same way I was, talking to himself, stopping at newspaper vending machines, rocking back and forth while waiting for the light to change, sudden bursts of speed followed by indecision and backtracking.
   Then I realized we had long since passed the Rite Aid. I wasn't running an errand any longer, I was stalking this poor guy. Maybe he was acting crazy because I was acting crazy.
   So when we got to the Office Depot I went inside, pretending it was where I wanted to go all along. I wandered around for a few minutes and by the time I left the store the odd little man was gone. I figure he must have remembered where his office was.