Sometimes the mind can become a hideously deceitful thing. Thank you dear granddaughter for taking care of your Grandpa. Now put everything away that he could possibly use to hurt anyone and keep an eye on him every single minute. I speak of what I know.  My Mom once threw herself out of her wheelchair by reaching down for a cat toy and we crushed the dining table trying to leap across it to catch her. It happens in the blink of an eye!
Bless you both and good luck!