My father is seeing shadow people all the time.

Excellent advice. Occurs most often with those close to death.
Uti causes incredible complications in the elderly.

IT does sound like a UTI, My dad would see these and they would get so strong an image it was like watching Men In Black by his description. Also he had Parkinson's and they were a good indication his medicines were out of balance. I would immediately check his records to see if he was getting meds late or early and that the staff was checking appearance of his urine. If it persisted for more than a couple of Days I would have them pull a urine sample and I would take it to the lab myself. Having standing orders from a Doctor can save you a lot of grief with staff.

Demons hover around suffering.

Holy Water. Blessed by a priest. Repent, cast out demons, and sprinkle holy water everywhere.. it works.

Have your father call on the name of Jesus Christ when
he has night terrors or sees the shadows.

Tell him to call on the name of Jesus Christ and for
the shadows to leave now in the name of Jesus Christ.

They will flee