The truck just all the sudden stopped

Thursdays are consistently one of the busiest afternoons for the Heating plus A/C repair and replacement business… Every one of us handle both commercial and residential calls, our day starts as soon as the sun is up and all of us do not stop until every job has been completed for the day, however i had an AC repair and a commercial boiler evaluation! The boiler evaluation took longer than I expected. It was my first time meeting with the shopper and the owner of the company had a lot of questions about our heating and AC services, then by the time I was on my way home, it was almost dark outside. The sun was starting to set and it was taxing to see when the sun was shining directly in my face. I was traveling about 45 mph on one of the back roads that leads to my condo when a truck just hastily stopped in front of me. The truck did not bother to use their turn signal and I did not see any brake lights either. The truck just hastily stopped and I slammed right into the back of it. The owner of the truck did not get out of the vehicle. I got out of my motorcar and started yelling at the driver for hastily stopping in the middle of the road. I saw the driver slumped over in the front seat. I did not see any other passengers in the vehicle. I instantly called 911. The driver of the other motorcar had a heart attack while on his way beach house from work, he might have died if I had not been there to call an ambulance.
air conditioning system