JK ROWLING has written a touching letter to the lone survivor of a shooting that left her entire family dead in the US.

The author reached out to teenager Cassidy Stay, whose parents and four siblings were killed in Houston, Texas, last month.

The 15-year-old quoted the Harry Potter character Albus Dumbledore at her family's memorial service last month by saying: "Happiness can be found even in the darkest of times, if one only remembers to turn on the light."

The Edinburgh-based writer responded to a Facebook campaign to arrange a meeting between her and the American teenager by sending Cassidy a series of gifts including a wand, a signed book and a hand-written letter "from Dumbledore".