Is it normal for a stranger tickling a boy he doesn't know?

I'm 19 years old now. This is a story from when i was 12. I never told anyone about this before, not even my parents because i was too embarrassed to do so, but i just couldn't get it out of my head since then. Not that i was hurt by it or something, i was just to curious about why someone does such an od action.
Anyway, to get to the point, there was a big park in my neighborhood, pretty far away from home, which i was visiting once in a while back then. My friends where never coming so far away (because they were chickens :P) but i used to very much enjoying going there when i was alone and just coming up whith stories for far away galaxies or how this place will be a million years from now and you know, child stuff :). It was like a small forest with very few people seen walking their dogs and away from the sight reach of any nearby building. I loved the endless hours of lonliness and peace.... But one day something super weird happened. It was noon, about 2:30. I was already super late for returning for lunch, so i couldn't find myshelf the courage to stand up and go listen to my mom's nagging. But i knew i had to start moving wanting it or not. Litteraly moments before starting heading home, a guy came; I couldn't tell his exact age but he didn't seem older than how i am now, perhaps even younger. He asked me if i wanted to participate in a recearch. I didn't really got scared (let's just say that i wasn't the type of kid that showed "respect" to older people; in fact i was "sticking my tongue" out every time an oportunity rose) but i just felt weird. Anyway i said yes and he told me to put my hand up and when i did he just.....tickled me(!?). This went on for a while and after that he told me to put my shoes of and he even tickled my feet. I was cautious the whole time, and i admit i may creeped out a little, but when he finished he just.....left. Before leaving i asked why he did that, in my desperate attempt to make a sense out of it, but he just tolb me something about an experiment and stuff i didn't really understood......maybe he purposely tryied not to make them understood. And as suddenly he appeared he JUST LEFT, leaving me with all those questions in my mind....
Now i know what the most common thought will be, but before you jump to this conclusion please take in mind that i was no fool, i would let no one have any kind of sexual interaction with me. I realize now that there were not much i could do if he was about to try anything, but i'm sure i would have at least scream or bite and scratch him to let me go, and i would imidiatelly report it to my parents and the police. Plus i may can't tell his exact age but he could even be underage too, and if no he definately wasn't more than 20. As far as i know pedophiles are usually not that young. I tried to follow him that day but i lost him. And after that, for many years i was wishing he might be back when i was sitting in that park, so i can ask him everything i wanted, but i never saw him again...... :(
Please tell me, was this action normal, and if so or not what reasons may have provoked it?