You have my sympathy as I have been there myself..
A few years ago we were having a downpour where the rain was bouncing knee high off the ground. It was so heavy I didn't want to run the 5 yards to my van. Soon the storm passed and blue skies appeared. I got in my van and drove around the corner and seen something quite strange, a dog was sat on the pavment in a deep puddle, motionless. It looked so odd considering the weather we had just had moments ago. It made me stop and get out to check what was wrong .. as I walked between the parked cars I found the cause, the dogs owner was lying on the pavement unconscious. I will never forget the sight the dog and its owner both had steam rising from them in the sunlight. The dog went for me as I attempted to assist the owner. I called for an ambulance and tried to calm the dog. After a couple of minutes the dog let me approach the owner, I checked his pulse and and couldn't find it. Never having attempted this before the ambulance controller talked me through pressing his chest and doing mouth to mouth. All the time I was doing it, I could hear sirens in the distance and wishing they would hurry up as I didn't seem to be getting anywhere. All of a sudden the man made a really long groan. I thought 'I've done it'.. I had brought him back to life. Sadly that sound has stayed with ever since.. I have since found out that that was the sound of him breathing his last.
The Police arrived before the ambulance, without asking what had gone on, one of them asked me to "clear the area and move on, as there was nothing to see" ..
Possibly the biggest put down I have ever experienced in my life.
For some time after the event I kept thinking, "if only I could have done more" .. as it kept bothering me I told my manager about my thoughts. She immedietely booked me on a First Aid training course and followed it up with annual refreshers.
.. dont think about that event much these days, not unless we have a torrential downpour !