What to do about an elderly senior who hits people? Is it okay to use a gentle rear bear hug to hold his arms down?

It's probably "OK" to use a gentle bear hug, but you are risking injury to yourself, and maybe him as well.

The answer is meds. Sorry but at this stage, there are not many if any good solutions. But it will keep him and those around him safe. A facility will not tolerate this type of behavior either.

Best of luck.

Maybe a punching bag he can hit whole seated may be the answer.

Freddynb: His physician needs to be notified of his behavior and possibly prescribe medication(s).

He needs to be on some medication.
This behavior is not acceptable.
He could injure himself or another.
He may be having hallucinations.
Be sure to consult with his medical professional immediately.

Personally, I would not want to restrain him as he might want to 'fight' more.
My client did this when hospitalized and going through medication changes to find what work(ed). She would lash out at the 'sitter' at her bed (24/7 perhaps). I said "Do not allow her to do that to you." I reported it to the nurse and they said they would could use restraints depending on what is going on. I said she is assaulting the sitter/caregiver. She needs to be restrained.

It is heartbreaking to see what happens to people when medicated - until the right amounts of the right drugs are found. Somehow, I was able to calm her down. She went from an almost tantrum to going to sleep when I said / asked: "M, are you hungry? What do you want?" Perhaps because she knew me, she relaxed immediately. Although I'll never forget that moment. It was like magic. I spoke softly and calmly to her.

Gena / Touch Matters

Most of the time hitting is a result of his frustration, anger, anxiety.
Medication can help with all of that.
Please consult with his doctor about this.

And you CAN get hurt trying to hold his arms down.
And HE can get hurt while you are trying to hold his arms down.

Look for the cues he gives BEFORE he gets to the point when he gets that angry and try to redirect.
Acknowledge his frustration and try to turn it.
Give him something else that will distract.
If he is getting angry because he does not want to do something that you want him to do then maybe back off for a bit. Let him calm down. Then try again.
Pick your battles (figuratively speaking not literally)

You need to get the anger under control BEFORE you try placing him in Memory Care. Most facilities will not accept anyone that has had violent outbursts. They typically want 60 to 90 days.

I agree with others on medication to alleviate his anger.

They are extremely strong when this mood comes on. It can catch you totally off guard as you would never expect that behavior from them. Consult his doctor for medication.

While a gentle hug or touch can be soothing, be warned that it doesn’t always work. Guard yourself.

If he is combative, LTC may not accept him for the safety of their staff and clients. As Alva mentioned he need medications first. Another option is to get him to the ER and tell them he is a danger to others and request a 72 hour hold called the Baker Act.

You need to see the doctor right away. He is severely agitated and distressed and needs medication.

You can't tell a broken brain to "calm down" because that part of their mind (reason, logic, empathy) are going or gone. Also, you put yourself in a possible dangerous position because elders with dementia can be shockingly strong. Move away from him when he takes swings.

Yes to having him checked for a UTI.

Yes to taking him to his PCP to discuss meds for agitation and aggression.

Consider that if this is a sudden change in behavior, it may be due to a UTI. Have that checked immediately.

Consider the fact that the quickest route to LTC placement is from a hospital. If dad is hospitalized and it it determined he needs placement, he jumps over all those folks on the waiting lists.

If he's become aggressive towards others and is putting himself at risk, that comes under the heading of "is a danger to himself and others". I would call the EMTs and have him gotten to the ER, both for evaluation of a UTI and to secure quick placement.

I'm including a Teepa Snow video that may give you some insights

https://www.youtube.com/watch?v=xNznZ2MnV3I

Sounds like you are doing what instinctively feels right for you and your father in this situation. You are helping to protect him and others around him.
I have one question for you, though; does your intervention actually help to calm him? You should be watching his reaction. It could be that he feels vulnerable and afraid, and being held down may cause him to be nervous and more agitated.
Hopefully you can find a LTC/ memory care that is experienced in handling his aggression. Unfortunately, the protocol is to NOT physically restrain a patient, and they will likely try and find a medication to calm or sedate him.
If the care facility is unable to manage the patient's behavior, they could kick him out.
Good luck to you and your family navigating your father's changing behavior and his unfortunate decline in health.