Should I be concerned?

Time to transfer him to a secure facility, or wake up dead. If he has any guns, get them out of the house.

This is one of those situations where you have to take care of yourself. Sleep separate. Even if a loved one has dementia, we have to protect ourselves from harm.

I would hope that your assessment is accurate in that you can be sure that is precisely what he is attempting to do. If that is the case, and in the middle of the night the behavior maybe only a bad dream, or perhaps a short phase of some other issue in the former life. What could that be? Some military training is involved with fracturing fingers during stressful times to avoid panic. I know it is a stretch. I would definitely be advised to break the cycle and try to avoid contact at that time. When he is asleep move out of the area, to safety.