Can a fired physician be appointed guardianship over my mother?

I have medical and durable power of attorney over my mother with dementia. I used my medical power of attorney to fire her primary care physician on the weekend during her hospitalization. He then threatened to file for guardianship. Can a fired physician be appointed guardianship over my mother. In front of 5 witnesses as he said this he pointed his finger in my face and I had to tell him to back away from my face twice. He said I was incompetent for firing him. I had a hospitalist doctor appointed until I could get my mother a doctor to replace him the next day. My mom was never without a doctors care. My mom has dementia and the medical and durable powers of attorney have been in force since before she got dementia and before he was her doctor. The hospital had record of this from the time of her admittance.