Dad with dementia has become hostile, angry with staff and residents of facility. Any advice?

MD consult at once. There are sometimes medications that can help. He will almost certainly have, without some controls, to be moved to a higher level of care, and unfortunately it will be a less caring level of care. I hope you will get some answers to what might help. But this is a medical need now.

If this is a sudden change in mental status, report it to his MD immediately. He could have UTI, he could have some other kind of infection, he may have had a stroke.

A change in mental status in a dementia patient needs to be investigated medically.