What are the end-of-life steps (as to who to contact) when an elderly person dies in the night?

Hopefully you have pre-arranged things with a funeral home. However, they cannot pick up the body until a death certificate is issued. Hospice makes this very simple. Without hospice you call 911, then you wait hours for the coroner to show up. Do not touch or move anything until the coroner says it is OK to do so. The coroner will want to talk to the MD to verify medical history. If no information is available, the coroner may order an autopsy. Detectives then arrive and ask a lot of questions; no one should leave until they are done.
Hospice is a lot less fuss.

One of the benefits of hospice care is you make one call, to them. They handle everything else.

First? call 911, standard process since there has to be a medical determination of death. Then give caregivers two phone numbers. One that will notify everybody that needs to know. The second number the person that will be handling all of the details. The caregiver is going to be very busy during this time.