Dads personality changed as he's gotten older. He's verbally insulting and very manipulative and controlling is this normal?

My dad is 87 years old and is in great physical health he walks 4 miles a day. He has always had a laid back personality and been a very caring father as long as I can remember. I have 3 older brothers and I am the youngest and only daughter..I guess you could say I have always been his little girl..Less than a year ago my mom passed away and myself and my husband lived a 1000 miles away and saw his mental state declining rapidly once my mom died. My husband and I both decided to move to live with him so he wouldnt have to be alone. At first things were great but now I am seeing a whole different side of my dad I never saw. He has become very demanding, when my husband and I go off on the weekends he calls my phone over and over and wants to know where in the h-ll we are and when we are coming home! When I get home its always the same we get the 3rd degree and lately have gotten into some nasty arguments..My dad has always been very caring towards me and very protective but lately he has become very verbally insulting towards me and my husband saying things to me I would have never thought my dad would ever say too me in a million years! He also lies alot which he never used to do he will do something and then blame me or my husband for it and even get mad and yell at us calling us liars saying we did it! He will do things that are just down right mean like this last valentines day he went into my drawer in mine and my husbands bedroom and throw away the valentines card my husband gave me..I couldnt believe he did that and I cried it hurt me very deeply. He will also yell at our dog he will tell her too GET when hes eating but then he will give her scraps..this confuses my dog she doesnt understand why she is being yelled at one minute then the next given food. He also picks the back of his head constantly it so bad that the back of his head looks like rare meat. He will take a shower every night but will wear the same clothes for 4 or 5 days..I have to sneak into his room and put clean clothes out for him..its embarrassing when we go off and he has food all over his shirt. My oldest brother lives about 1100 miles away so he is only able to come down once every few months, but my other brother lives hear but he never calls or comes by my dad only sees him if he goes out to his house its terrible..It really hard seeing a man I have admired and look up to my whole life turning into a mean demanding gumpy old man..I guess I wrote this in the hopes that I am not alone out there that other people go through this with their elderly family members also..I cant help but wonder if my dad is getting dementia or is this just part of getting old..I would appreciate any stories or comments anybody would like to share with me..Thank you and God Bless..