Is the patient on hospice care? If so, I would ask them about it. My brother, sister, and I were there when our mother died. Hospice had told us to call them when that happened. We did, and they came and took care of a lot of things. They prepared a death certificate, asked us what funeral home we planned to use, then called the funeral home to come get my mother's body. Hospice was tremendously helpful.
We were told to call hospice first. They sent someone to examine Mom and pronounce her dead, and then they called the funeral home we had selected. From what I read above, that seems to be the regular practice. If not in hospice, then I would call 911.