Out too fast and beware the FOP's

First off I just don't like old people. At all. I have many reasons but their constant ignorance bewilders me. Me, a big 200lb monster running at them, obviously on one side of the sidewalk, these fuckers have the indecency to not move, or worse, provoke me by moving into my "lane". If I ran any of them over, I would break all their bones. Jesus I tell you, one day I am not going to move out of the way and just keep running hard.
Now that that is out of the way, I got home from work and was ready to run. My back/hip issue was calmer today and I was looking forward to it. I laced up and headed out in some pretty nice weather considering the shit we have had lately, it was 6C and sunny. I started off real well, comfortable and fast. My second km was even faster and I was noticing that I was already labouring with a long way and some serious hills still to go. I laid off a bit and tried to calm down some. I felt great physically but my HR was up and I could feel it. I worked the first hill best I could and took the downhill easy to try and recover. My pacing was good over the next 3k until the last set of hills and the early pace caught up with me. I just muscled my way through it. The last km in site I was tired, pissed off and just wanted to finish, so I hurried up and put the hammer down. No FOP's in my way so I was able to run a 4:22km after all the crazyness before. Felt good today because all my pacing was done under 5 minute kilometers which is a first for me. 47:45 ~ 10 km, 4:47 per km.