Officers found Matthew Williams, 34, attacking Ms Yemm in the Sirhowy Arms Hotel in Argoed, Caerphilly county on 6 November 2014.
He was stunned with a Taser and arrested at the scene but later died.
Healthcare Inspectorate Wales is looking at the mental health support Williams received before the killing.
Williams was known to mental health services at Aneurin Bevan, Abertawe Bro Morgannwg and Cardiff and Vale University health boards.
The health watchdog said its independent review would investigate the care, medical history and events surrounding the killing in a bid to "provide an understanding and background to the fatal incident".
The review will try to identify any change in Williams's behaviour, look at documents including risk assessments, assess how different agencies worked together and and interview staff involved in Williams's care.
It has published the terms of reference for the independent review, which was ordered by the Welsh government.
Inquests into Williams's and Miss Yemm's deaths are due to be held in the autumn.
A report to ensure "lessons are learnt" after a homeless prison leaver killed 22-year-old Cerys Yemm is to be published in early 2016.