The Circle House

There was a king, queen,princess,and a prince. And they lived in a big circle house. They were going on vacation to the lake but the prince decided not to come. When the rest of the family got back from the lake they found the prince lying on the floor dead. The suspects are the butler the maid the chef and the nanny. The butler said he gave him a drink of water. The maid said she was in the corner sweeping. The chef said he was chopping up some vegetables and the nanny said she just read him a story to help im go to bed. Who killed the prince?