One year old Hitting

Ashley

My one year old has recently started hitting. She hits the cats and she hits us. She also has started hitting her older sister with objects and her hand. Her older sister is 5 and has been in tears many times at the hands of her little sister. We never had this problem with our oldest and have no idea how to get her to stop. We have tried modeling gentl touches with our cats and petting nicely and she still hits. Any advice out there?