A woman had reported her apparent killer to police just one week before she was fatally stabbed by him.
Donna Wilson had reported Clarke the previous weekend
Staffordshire Police said Donna Wilson, who was stabbed on Sunday, had reported an assault and theft by Shaun Clarke, 45, the previous weekend.
Ms Wilson, 30, of Burton, died on Monday - Clarke's body was later found in woodland. It is thought he killed Ms Wilson before taking his own life.
It also emerged Clarke had served 16 years for an earlier murder.
A statement from Staffordshire Police said the force "had contact with both Shaun Clarke and Donna Wilson shortly before their deaths".
"In line with legislation on police contact in such circumstances, the force has referred the matter to the Independent Police Complaints Commission.
"We can confirm that Donna Wilson attended Burton Police Station on the evening of Saturday, 13 January to make a complaint against Shaun Clarke of common assault and theft. This was being investigated by Staffordshire Police."
Staffordshire Probation Service has also launched an inquiry as Clarke was under its supervision since being released from Sudbury Open prison, Derbyshire, in 2003 - 16 years into a life sentence for a murder.
Chief probation officer Rob Mandley said: "I can confirm that Mr Clarke was sentenced for murder in 1987 - life imprisonment. He was released from prison in May 2003.
"We are working closely with Staffordshire Police and hope to give some more details a little later."
Ambulance staff treated Ms Wilson for stab wounds when called to St Stephen's Court, Burton, on Sunday evening. She died in hospital the following morning.
The body of Clarke, 45, of Shakespeare Road, Burton, was found at Branston Water Park, Burton, on Monday, two hours after Ms Wilson's death.
Staffordshire Police are treating Ms Wilson's death as murder but believe Clarke's death was not suspicious.