Toddler keeps escaping from the house

Any thoughts or suggestions? My nephew is 3 and since my sister has moved over 3 months ago my nephew has been escaping from the front door and the garage door and bolting it outside. He repeatedly says he wants to go home and my sister tells him he is home? We are confused and worried about his safety. She has baby gates and just bought safety locks but I never seen this type of behavior before and find it very strange.