How can things return to 'Normal' when this isn't 'Normal'

My seventeen year old son, Bryn, died nearly a month ago when his car hit a horse that had got loose from a house close to where we live and strayed onto the road. We live on an acreage, so we're somewhat accustomed to there being a deer or moose on the road occasionally, and we know which roads to look out for. Bryn hit a freakin horse, on a road that rarely has any animals on it. If he had hit a moose or a deer, the result would probably have been the same but it would have made more sense somehow. But someone's horse? It's so twisted. He never did like horses.

I work for a good company and with a lot of kind, considerate people. It doesn't surprise me at all these people are coming to welcome me back after my bereavement leave and ask how I am doing. I wish they would leave me alone though. What do they expect me to say; that I'm fine? I just buried my son. There are reminders of him everywhere. I didn't protect him from injury and I couldn't fix it or make him better. He's dead and it's permanent. I feel screwed up in my head. I'm trying to smile when really I'm struggling not to cry. I have a splitting headache. I don't want to be here. 

Today is my second day back at work since Bryn's accident. Not sure things are going that well. Another challenge just to get through the day when everything work related just seems so meaningless. An invisible force is trying to push me back onto the 'normal' path, back at work, 9 to 5. How can my wife, my oldest son or I get back onto the normal path though? No parent should have to deal with their child's funeral. No nineteen year old should have to deal with their younger brother's death. What part of this is normal? It isn't normal. It isn't the way it's supposed to be. We shouldn't be getting back onto the normal path; everyone else should be getting off it.