Hit & run vs Self defence

Seems to me like I never realize I've had a near death experience until after one just about happens. I don't know how i manage to go through life in such an oblivious way, I've often likened myself to an absent minded professor. My family tell me I just have a short attention span. This morning at 2:30am I was on my way to work, (a 4hr shift, it seemed like almost a waste of time) when a guy stepped out in front of my car just as I was about to go straight over the pedestrian crossing on a road not far from my house. Since it was dark and he was wearing a hoodie i didn't see him until I'd passed him, good thing he stopped or I would have mowed him down. After going past and getting a fright that I'd nearly hit someone I started thinking about the situation. He was (he? I don't even know) with someone else, both of them wearing hoodies. And they were standing in the middle of the road staring after my car for ages. Why wouldn't they just get off the road? Not to be rude, but if i did run down someone who looked like a gang member/ someone who could be trying to car jack me, could I be held responsible? Or could I claim self defense? After all, what kind of sane person would try to step in front of a car with its lights on in the middle of the night when there is no traffic anyway? Why would anyone want to stop a car at that time, except someone who was up to no good? And if I had hit him and then kept going, couldn't I just call 111 and tell them "Oh sorry, I hit someone. No i didn't stop. A single female in the middle of the night? I don't think so. I'll tell you where it was and you can send a cop to go check on him." My friend from South africa said over there, people will deliberately lie on the road so that cars slow down then they can kill the driver and steal whatever they have on them. It will be a sad day when that starts happening here.