question

I'm a volunteer fire fighter and I have a full time job. Recently I was on scene of a code 4 vehicle accident, we had to cut the roof off of the car to get the patient out and in the process I dislocated my shoulder twice. I popped it back in both times an nothing was torn or broken but I couldn't raise it above my head. I went to the hospital to get x-rays and I went to an orthopedic doctor. I was told not to come in to work because of my restrictions, and I have only been at this place for a month. It was my day off when I went on this rescue run. I was informed by HR that my position will be filled because it needs to be filled. I was also informed after my next orthopedic doctor's appointment if I'm able to work and if theres still a position available I'll still have a job if not then i will be let go. Is it right for me to be fired for this?