What is the true story why the shrieking shack is known as the most haunted house in Britain?

The shrieking shack is a fictional place created by J. K. Rowling for her Harry Potter series. What you see in the movies is a shack built on the set. The reason it was said to be the most haunted building in England is because it was built for Remus Lupin, a werewolf, when he was a student at Hogwarts. However, no one knew he was a werewolf, save his three best friends, so they thought the shrieks coming from the shack were created by ghosts.