WARNING: Distressing content.

An aged care resident has been charged after allegedly assaulting an elderly dementia patient at a facility in Sydney’s south-west.

Much-loved husband and grandfather John, 87, was allegedly attacked by another resident on Wednesday night, causing serious head injuries.

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WATCH THE VIDEO ABOVE: Dementia patient bashed at Sydney aged care home

“Absolutely horrific. We’re all in a lot of shock. I’ve never seen anything like this before. I’ve never seen anybody this beat up,” John’s daughter Margaret told radio station 2GB.

The elderly dementia patient was found around 9pm on Wednesday on a verandah of the HammondCare centre in Hammondville with extensive injuries.

Police were called and paramedics attended to take the 87-year-old to Liverpool Hospital where he remains in a serious condition.

“This was not a minor altercation,” his daughter said.

“This was not a push or a scuffle.”

NSW Police issued a statement on Thursday evening that a 69-year-old man was arrested at the facility around 3pm.

“He was taken to Liverpool Police Station and charged with assault occasioning actual bodily harm (DV),” police said.

“The man was later taken to Liverpool Hospital where he remains under police guard.”

He was refused bail to appear via a bedside hearing at Liverpool Local Court on Friday.

HammondCare says an investigation is now underway into how John was assaulted without anyone seeing or hearing it.

“We had over adequate amount of staffing on that night but they were attending to their normal duties,” HammondCare Executive General Manager Jenny Summerton said.