What should I do about my dad who leaves pans on the stove with burners on and forgets?

Dad leaves pans on the stove with burners on and forgets he was doing that resulting in quite a few close calls. What should I do?

We have had this issue in the last few months where Dad will heat up something at full flame on the stove then takes a nap or goes to the yard to work on his trees. End result is a burned pan and a very close call. My husband has already suggested to him that when he is using the stove to stay there until he is done and turn the stove off. He did it again on Monday while we were out of town. We were 40 minutes from home when I called to check on him and everything was fine. As we pulled up to the house we could see into the back yard and there he was crawling on his hands and knees. I entered the house and as I walked through the kitchen I noticed there was a pot on the stove with the flame on high and the contents bubbling and sputtering. He was still trying to get up when I got to him. When I told him about the stove he was not concerned he just asked if I turned it off. I could only picture the house burning down if we had taken longer to get home. It is to the point that we are scared to leave him alone for fear he might burn himself or burn the house down.