I've worked and volunteered in nursing homes for 8 years in the actual secured dementia ward. Locked, security coded and fully gated. This type of distressing incidents happen quite a lot. Residents aren't themselves. They act in all kinds of odd ways and can get aggressive, shout, hit staff, wander around the corridor all night upset over something that has set them off. Could be anything and no one knows what it is unless it's a routine occurrence.
I have seen some very disturbing things and wanted to get my mother outa there. It seemed too confronting for the fairy tale placid place I thought she would see out her last years in.
Eventually, if you spend enough time in the ward, you realise 90% of the staff are angels and can handle these incidents as part of the job, as well as shower and toilet an unco-operative mentally challenged frail man or woman who resist at every turn. The staff deserve a huge pay increase.
I am assuming these were relatively new staff who couldn't handle the situation and called police.
The nursing home need to be investigated along with the police so that these types of incidences can be handled better by everyone.