The killing of Shambuka appears in the Valmiki Ramayana, Book 7, the 'Uttarakanda' [Final Chapter], sargas 73-76, in the Adhyatma Ramayana version of Ramayana [REF].
Scholars such as Purushottama Candra Jaina,[REF] and John Brockington[REF] writes that this story "is of late origin".