JK Rowling's written to a US teenager who quoted from a Harry Potter film at a memorial for her family who were shot dead by a gunman.

She told mourners: "Happiness can be found even in the darkest times if one only remembers to turn on the light."

The words were orignally spoken by Harry's headteacher Albus Dumbledore in The Prisoner Of Azkaban. 

A spokesman for Rowling said the 49-year-old author had sent the letter, but declined to confirm if there was a plan for the pair to meet.

"We can confirm that JK Rowling was in touch with Cassidy Stay, however, the contents of the letter remain private."

Ms Rowling is said to have written to the teen as the character Dumbledore.

Cassidy's parents, Stephen and Katie, were killed on July 9th, along with her four siblings.

Cassidy suffered a skull fracture and lost part of her finger during the shooting but "played dead" until the alleged shooter, Ronald Lee Haskell, had left the home.

She then called the police and later identified Haskell, who is her uncle by marriage.